Chimera

Chimera is a Windows ransomware family known for targeted email-based distribution against small companies. It encrypts files on available disks and appends a .crypt-style extension, then presents an HTML ransom note in English or German, including full-screen display through Internet Explorer. Chimera became notable for early use of leak-style extortion threats, claiming that stolen files and credentials would be published if payment was not made; however, examined samples indicated that this exfiltration threat was not actually implemented in those builds.

The malware has been documented as a multi-stage loader chain consisting of a packed .NET stub, an intermediate loader, and a core payload. The stub decrypts and launches the next stage using RunPE-style or manual-mapping techniques, while the core component performs host identification, encryption, ransom-note handling, and network communications. Chimera generates victim-specific identifiers from host characteristics, collects basic system information, and uses asymmetric cryptography to protect per-file symmetric encryption keys. It processes files in chunks and communicates over the Bitmessage peer-to-peer protocol rather than relying solely on conventional centralized command-and-control infrastructure.

Separately from the ransomware family, Chimera is also tracked as an intrusion set associated with enterprise post-compromise activity. That activity includes credential abuse, password-hash dumping for pass-the-hash, bookmark and email collection, network-share discovery, domain-trust discovery, network scanning, scheduled-task persistence, timestomping, HTTPS and DNS-encapsulated command-and-control, and exfiltration to attacker-controlled channels and cloud storage. Those intrusion-set behaviors should not be conflated with the original ransomware family unless specifically distinguished in analysis.