Cyberespionage groups have been using ransomware as a tactic to make attack attribution more challenging, distract defenders, or for a financial reward as a secondary goal to data theft.

We recently discovered ransomware, which performs MSDTC service DLL Hijacking to silently execute its payload. We have named this ransomware CatB, based on the contact email that the ransomware group uses. The sample was first uploaded to VT on November 23, 2022 and tagged by the VT community as a possible variant of the Pandora Ransomware. The assumed connection to the Pandora Ransomware was due to some similarities between the CatB and Pandora ransom notes. However, the similarities pretty much end there. The CatB ransomware implements several anti-VM techniques to verify execution on a “real machine”, followed by a malicious DLL drop and DLL hijacking to evade detection.