Microsoft issued a warning on Thursday May 20th about a large “email campaign” that’s issuing a Java-based STRRAT malware that steals personal data from contaminated and hijacked systems while masquerading as a ransomware infection.
The Microsoft Security Intelligence team stated that this RAT is infamous for its ransomware-like behaviour of appending the file name extension ‘.crimson’ to files without actually encrypting them. The new movement of cyberattacks was spotted by the company last week, the attacks originates with spam emails sent from the compromised email accounts with “Outgoing Payments” in the subject line, then the recipients are encouraged to open malicious PDF documents that claim to be transfers, but instead connects to a rogue domain to download the STRRAT malware.
Besides establishing connections to a command-and-control server during execution, the malware comes with a range of features that allow it to collect browser passwords, log keystrokes, and run remote commands and PowerShell scripts.
STRRAT was first noticed in the threat landscape in June 2020 by German cybersecurity firm G Data observing the Windows malware (version 1.2) in phishing emails containing malicious Jar/Java Archive attachments. The RAT has a emphasis on stealing records of browsers and email clients, and passwords via keylogging.
Its ransomware capabilities are at best rudimentary in that the “encryption” stage only renames files by suffixing the “.crimson” extension. “If the extension is removed, the files can be opened as usual,” Kahn added.
Microsoft observes that version 1.5 is more complicated and flexible than prior editions, this suggests that the attackers following the procedure are aggressively working to manage their toolset. The hoax encryption behaviour remains unchanged, which suggests that the group may be aiming to make quick money off unsuspecting users through the use of extortion/coercion.