Pierluigi Paganini September 04, 2024

A group of hacktivist known as Head Mare took advantage of the recent CVE-2023-38831 WinRAR flaw in attacks against organizations in Russia and Belarus.

Kaspersky researchers reported that a hacktivist group known as Head Mare exploited recently disclosed WinRAR flaw CVE-2023-38831 in attacks against organizations in Russia and Belarus.

Head Mare has been active since at least 2023 exclusively targeting companies in Russia and Belarus. The group announced its victims on X and also leaked internal documents stolen during attacks on the same social network.

The group relies on modern techniques for gaining initial access to systems. Kaspersky reported that they exploited the CVE-2023-38831 WinRAR vulnerability in WinRAR, which could lead to arbitrary code execution by tricking the victims into opening a specially crafted archive.

Head Mare has targeted nine victims across various industries, including government institutions, transportation, energy, manufacturing, and entertainment. Their primary purpose appears to be causing significant damage to companies in Russia and Belarus. Unlike some hacktivist groups, Head Mare also encrypts victim data and demands.

Below is a list of software employed by the group in its attacks:

• LockBit ransomware;
• Babuk ransomware;
• PhantomDL;
• PhantomCore;
• Sliver;
• ngrok;
• rsockstun;
• XenAllPasswordPro;
• Mimikatz.

“In their attacks, Head Mare mainly uses publicly available software, which is typical of most hacktivist groups targeting Russian companies in the context of the Russo-Ukrainian conflict.” reads the report published by Kaspersky. “However, while some hacktivists have no proprietary developments in their toolkit at all, Head Mare uses their custom malware PhantomDL and PhantomCore in phishing emails for initial access and exploitation.”

After execution, the malware tools PhantomDL and PhantomCore connected to the attackers’ C2 servers to identify the domain of the infected host. Attackers distributed the two malware via phishing campaigns in the form of business documents that had double extensions (i.e., решение №201-5_10вэ_001-24 к пив экран-сои-2.pdf.exe).

Dynamic analysis in Kaspersky Sandbox shows that PhantomDL connects to a specific C2 server, while PhantomCore connects to different C2 servers and checks the host’s domain. Although some PhantomDL and PhantomCore samples were found, it’s uncertain if they belong to the same activity cluster as those used in Head Mare’s attacks.

The hacktivists used several methods to maintain persistence in the system, including a Windows registry keys and scheduled tasks. 

The researchers also observed the group using the open-source C2 framework Sliver. The framework was used to manage compromised systems allowing attackers to carry out malicious activities such as executing commands, managing connections, and gathering data.

The last stage of the attacks consist in deploying either LockBit or Babuk depending on the target infrastructure.

“The tactics, methods, procedures, and tools used by the Head Mare group are generally similar to those of other groups associated with clusters targeting organizations in Russia and Belarus within the context of the Russo-Ukrainian conflict.” concludes the report. “However, the group distinguishes itself by using custom-made malware such as PhantomDL and PhantomCore, as well as exploiting a relatively new vulnerability, CVE-2023-38831, to infiltrate the infrastructure of their victims in phishing campaigns. This is an important aspect that Russian and Belarusian organizations should pay attention to: attackers are evolving and improving their TTPs.”

Pierluigi Paganini

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(SecurityAffairs – hacking, hacktivist)