Cs-137 ransomware group
Cs-137 is one of the extortion operations we watch continuously. This page covers what is known about the group and the current state of its leak site.
Who they are
Cs‑137 is a newly observed ransomware strain that first appeared in January 2025. It employs the ChaCha20 cipher for encryption and appends obfuscated filenames with a random 10-character alphanumeric identifier while preserving the original file extension. In its current testing phase, it drops a ransom note with a randomized filename (e.g. ABCDEF-README.txt) and sets a randomly named image file as the desktop wallpaper. The note references a Tor-based extortion portal—though access is not yet active, indicating the operation’s early development stage. The strategy suggests single-extortion behavior, focused on disrupting access rather than data theft or leak threats.
Current status
Cs-137's leak site is not answering. Sites go dark for infrastructure trouble, a deliberate quiet period, or a takedown, and a good number return weeks later under the same name, so the entry stays on the list either way.
Which organisations this group has named, and when, is part of the SINON platform rather than this page. Create an account to search it, or to be told automatically if a name you care about turns up.
Sectors targeted
This group does not state an industry on its site, so we have nothing reliable to report. Most crews are opportunistic rather than sector-specific in any case — they hit what they can reach.
Watching for your name
If Cs-137 posts your company, a supplier or a subsidiary, you want to hear it from us rather than from a journalist. SINON checks these sites continuously and alerts on the names you give it.
Start monitoring