Sysrv botnet Attack Windows, Linux Servers with New Exploits – Microsoft

Using vulnerabilities in Web frameworks and WordPress, the Sysrv botnet now targets vulnerable Windows and Linux servers to deploy crypto-mining malware.

This new variant (tracked as Sysrv-K) discovered by Microsoft may now scan WordPress and Spring deployments for unpatched code.

Here’s what the Microsoft Security Intelligence team stated:-

“The new variant, which we call Sysrv-K, sports additional exploits and can gain control of web servers. These vulnerabilities, which have all been addressed by security updates, include old vulnerabilities in WordPress plugins, as well as newer vulnerabilities like CVE-2022-22947.”

This vulnerability (CVE-2022-22947) can be exploited by a remote attacker to gain execution of code on unpatched hosts by exploiting the Spring Cloud Gateway library.

Technical Analysis

As part of these newly added capabilities, Sysrv-K searches for WordPress configuration files and their backups in order to discover database credentials, which can then be used to infiltrate web servers.

Security researchers from Alibaba Cloud (Aliyun) had first discovered this malware in February after it was active since December 2020.

Besides gaining the attention of researchers from Lacework Labs and Juniper Threat Labs, this malware also crossed the radar screens of security researchers in March.

Sysrv exploits the vulnerabilities in Linux and Windows enterprise servers by infecting them with Monero (XMRig) miners, as well as self-spreading malware.

This botnet infiltrates web servers by exploiting vulnerabilities in web applications and databases which can lead to them being compromised. Here are the applications and databases that are exploited:-

• PHPUnit
• Apache Solar
• Confluence
• Laravel
• JBoss
• Jira
• Sonatype
• Oracle WebLogic
• Apache Struts

Upon launching its own payloads and killing competing cryptocurrency miners, Sysrv also spreads over the network automatically. This type of malware is spread by brute force attacks using many of the private keys collected from the servers infected with it.

The aim of this component is to add more vulnerable Windows and Linux systems to its army of Monero mining bots by aggressively scanning the internet for vulnerable machines.

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