Cybersecurity researchers have discovered a previously undocumented modular malware framework codenamed Avalon that's distributed by means of a multi-stage phishing chain capable of bypassing traditional security controls.
Avalon combines credential collection, lateral movement, remote access, recovery disruption, and ransomware execution, bringing together diverse functions under one umbrella. The ransomware component has been internally named CrownX.
"The attack began with a spoofed legal document email directing recipients to a password protected archive on Proton Drive," Blackpoint Cyber researchers Nevan Beal and Sam Decker said. "Malicious content was embedded inside an ISO image rather than attached directly, reducing the likelihood of detection at the email layer."
Should the email recipient interact with a document-themed Windows Shortcut ("Secure Document CA-283505.pdf.lnk") inside the mounted image, it triggers a staged malware sequence that culminates in the deployment of Avalon. Specifically, the shortcut runs a command to launch an MSBuild project located in the ISO image.
The MSBuild project, for its part, loads an embedded .NET assembly, which then interferes with the regular functioning of Event Tracing for Windows (ETW) to reduce forensic visibility and download a next-stage payload over HTTPS responsible for launching Avalon.
