The CLR SqlShell malware strain is a significant threat to Microsoft SQL (MS SQL) servers. It is a type of malware that has been created and deployed by attackers to exploit poorly managed MS SQL servers. This malware strain can deploy multiple attacks, including cryptocurrency miners and ransomware. By taking advantage of vulnerabilities in the system, the attackers can install the malware and execute malicious commands remotely. In this article, we will explore the CLR SqlShell malware strain in detail and discuss how it works.
Overview of CLR SqlShell malware strain
The CLR SqlShell malware strain is a specific type of malware that is designed to target MS SQL servers. This malware can be used to deploy various types of attacks on the server, including cryptocurrency miners and ransomware. Essentially, this malware is a variation of a web shell, which is a hacking tool that is commonly installed on web servers. The similarities between a web shell and the CLR SqlShell malware strain are significant, and we will explore those further later in the article.
Types of attacks deployed by the malware
The CLR SqlShell malware strain is designed to deploy multiple types of attacks. Two of the most common types of attacks are cryptocurrency miners and ransomware. Cryptocurrency miners use the infected server’s processing power to mine for cryptocurrency, which can be extremely profitable for attackers. On the other hand, ransomware attacks encrypt the server’s data and request payment in exchange for the decryption of the data.
Similarities between SQL shell and web shell
The CLR SqlShell malware strain is similar to a web shell in several ways. Essentially, both web shells and SqlShell are hacking tools designed to allow attackers to gain remote access to the compromised server. Both tools can execute commands remotely and download additional malware or tools. However, there are also several differences between the two, which we will explore later in this article.
Understanding CLR Stored Procedures
CLR stored procedures refer to stored procedures that are written in a .NET language like C# or Visual Basic. These stored procedures can be executed in MS SQL Server, and they can be used for a variety of purposes. The CLR SqlShell malware strain uses CLR stored procedures to execute its commands and deploy attacks. Adversaries can write customized CLR stored procedures that execute specific commands remotely.
The use of xp_cmdshell command to install SqlShell in MS SQL servers
One of the primary methods that attackers use to install the CLR SqlShell malware strain on MS SQL servers is by using the xp_cmdshell command. The xp_cmdshell command enables the execution of shell commands on the server. Attackers may use brute force or dictionary attacks to gain access to the server’s administrative credentials and then execute the xp_cmdshell command remotely.
Techniques used by adversaries to execute malware
Adversaries use several techniques to execute malware on MS SQL servers using the CLR SqlShell malware strain. These techniques include the use of xp_cmdshell commands, the execution of OLE stored procedures, and the use of CLR stored procedures. Essentially, these techniques allow attackers to execute commands remotely and deploy malware on the compromised server.
The use of SQL Shell routines to download next-stage payloads
Once the CLR SqlShell malware strain is installed on the server, attackers can use it to download next-stage payloads. These payloads can be anything from Metasploit to cryptocurrency miners. The attackers can then use these payloads to execute more sophisticated attacks on the server, including privilege escalation and persistence.
Examples of different adversaries using SQL Shells
Various adversaries have used different versions of the SqlShell malware strain, including SqlHelper, CLRSQL, and CLR_module. These adversaries may have different goals for their attacks, such as deploying ransomware, stealing data, or using the server for cryptocurrency mining.
Installation of additional malware through SQLShell
Once the CLR SqlShell malware strain is installed on the server, adversaries can use it to install additional malware. This malware can include backdoors, coin miners, and proxyware. Essentially, attackers can use the compromised server and its resources for several different purposes.
Execution of malicious commands by SQLShell
Finally, the CLR SqlShell malware strain can execute malicious commands received from threat actors. This is done in a way that is similar to a web shell, using the compromised server’s resources to execute commands remotely.
In conclusion, the CLR SqlShell malware strain poses a significant threat to MS SQL servers as it can deploy multiple types of attacks, such as cryptocurrency miners and ransomware. Attackers can use various techniques, including xp_cmdshell commands and CLR stored procedures, to execute malware. Once the malware is installed, the attackers can download next-stage payloads and install additional malware. Finally, the malware can execute malicious commands remotely, which poses a significant risk to businesses and organizations using MS SQL servers. It is crucial to stay vigilant when managing MS SQL servers and use multiple layers of security to protect against these attacks.