Ukraine’s Computer Emergency Response Team has warned of a new cyberattack campaign being run by Russia-linked threat actors. The group, known as APT28, is using Signal chat messages to deliver two new malware families to targets. These new malware variants have been named BEARDSHELL and COVENANT by the cybersecurity researchers who first discovered them.
The threat actors are sending messages on the Signal platform to deliver a macro-laced Microsoft Word document. When this malicious document is launched by a victim, it immediately drops two different malicious payloads. The embedded macro also makes specific Windows Registry modifications to ensure that the malware achieves system persistence. The primary task of the first payload is to load the shellcode from a PNG file to execute COVENANT.
The attacks were first observed in March 2024, but the initial infection vector was not known until recently.
The COVENANT malware framework subsequently downloads two more intermediate payloads that are designed to launch the BEARDSHELL backdoor. BEARDSHELL’s main functionality is to download and execute PowerShell scripts, communicating via the legitimate Icedrive cloud storage API. In some of the earlier attacks, a screenshot-taking tool that has been named SLIMAGENT was also observed. State organizations are now recommended to keep an eye on network traffic associated with specific cloud service domains.
This disclosure comes as CERT-UA has also revealed APT28’s targeting of outdated Roundcube webmail instances in Ukraine.
The group sends phishing emails that weaponize several known vulnerabilities to execute arbitrary JavaScript code on the server. The malicious code is capable of exfiltrating the victim’s entire address book and also their current session cookies. In all, similar phishing emails were sent to the email addresses of more than forty different Ukrainian organizations.
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