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Fileless, Code-Injecting Ransomware SOREBRECT Emerges

A newly discovered ransomware family incorporates a combination of fileless attack and code-injection, Trend Micro security researchers warn.

A newly discovered ransomware family incorporates a combination of fileless attack and code-injection, Trend Micro security researchers warn.

Dubbed SOREBRECT, the threat was initially spotted a couple of months ago, when it managed to infect the systems and networks of organizations in the Middle East. The ransomware packs unusual encryption techniques, is abusing the PsExec utility to leverage code injection, and also focuses on remaining stealthy, the security company says.

The ransomware was fitted with a self-destruct routine that turns it into a fileless threat: it injects code into a legitimate system process before terminating its main binary. Furthermore, it goes to lengths to delete the affected system’s event logs and other artifacts in an attempt to hinder forensic analysis and prevent researchers from tracking the threat’s activities.

When discovered, SOREBRECT had a low distribution and concentrated on Middle Eastern countries like Kuwait and Lebanon. By early May, however, it was already found on computers in Canada, China, Croatia, Italy, Japan, Mexico, Russia, Taiwan, and the U.S., infecting industries including manufacturing, technology, and telecommunications.

“Given ransomware’s potential impact and profitability, it wouldn’t be a surprise if SOREBRECT turns up in other parts of the world, or even in the cybercriminal underground where it can be peddled as a service,” Trend Micro says.

During attacks, the malware abuses PsExec, a legitimate Windows command-line utility used by system admins to execute commands or run executable files on remote systems. This, researchers say, means that attackers are already in the possession of administrator credentials or that the remote machines were exposed or brute-forced.

SOREBRECT, however, isn’t the first ransomware family to misuse PsExec, with SamSam, Petya, and its derivative, PetrWrap also abusing the utility to install the ransomware on compromised servers or endpoints. The new threat, however, maliciously deploys PsExec and performs code injection.

“It injects its code into Windows’ svchost.exe process, while the main binary self-destructs. The combination is potent: once the deployed ransomware binary finishes execution and self-termination, the injected svchost.exe—a legitimate Windows service-hosting system process—resumes the execution of the payload (file encryption),” Trend Micro explains.

The researchers also argue that the ransomware’s code injection capability makes the attack more effective compared to using the Remote Desktop Protocol (RDP). Through PsExec, attackers can remotely execute commands, instead of providing a log-in session or manually transferring the malware to the target machine.

The ransomware also uses wevtutil.exe to delete the system’s event logs, and vssadmin to delete shadow copies, thus covering its tracks and preventing users from recovering their files. The malware also uses the TOR network to communicate with its command and control (C&C) server.

The threat can also encrypt files on network shares, the researchers warn. For that, it scans the network for asset discovery and enumerates open shares, including folders, content or peripherals that are readily accessible through the network. Next, it initiates a connection to the discovered share and, if both read and write access are available, it encrypts it.

To stay protected, IT/system administrators and information security professionals are advised to restrict user write permissions and limit privileges for PsExec. As usually, keeping files backed up at all times and both systems and networks updated can prove helpful in case of an attack. Training employees on security and deploying multilayered security mechanisms are also highly important.

Related: Fileless Ransomware Spreads via EternalBlue Exploit

Related: Recent Fileless Attacks Linked to Single Framework, Researchers Say

Related: Legitimate Tools Abused For Fileless Infections

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

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