Cactus Ransomware Recovery: What's Recoverable

Cactus surfaced around March 2023, using a double-extortion model with victim communication over Tox. It appends a .cts1 extension to encrypted files, with a ransom note named cAcTuS.readme.txt, and has been linked by Microsoft to malvertising campaigns as a delivery method alongside VPN application vulnerabilities.

Once inside, Cactus harvests credentials via LSASS memory dumps and browser credential theft, maps the network with Nmap and SoftPerfect NetScan, moves laterally via RDP and SSH using tools like Chisel and AnyDesk, and disables security tools before deploying Cobalt Strike and the ransomware payload itself.

Because entry can be as ordinary as a compromised VPN endpoint or a malvertising click rather than a targeted spear-phish, organizations sometimes have less advance warning than with more research-intensive groups. The recovery approach is the standard one regardless of entry vector: preserve current state, don't restore into the same credentials or network segment, and assess the underlying storage before assuming what's encrypted is unrecoverable.