Detecting Unusual Image Loads of vsstrace.dll

This detection focuses on the unusual loading of 'vsstrace.dll' by non-standard processes on Windows systems. While 'vsstrace.dll' is a legitimate component of the Volume Shadow Copy service, its loading by unexpected executables outside of system-trusted directories or known backup software can be indicative of post-exploitation activity. Attackers often attempt to interact with, enumerate, or delete shadow copies as part of an Impact phase, typically to hinder recovery efforts during ransomware operations. Defenders should monitor for processes that load this library from unauthorized paths, particularly those that do not align with established baseline behavior for system administration or backup software.

Impact

Successful unauthorized interaction with Volume Shadow Copy components can facilitate the deletion or corruption of system backups, significantly hindering disaster recovery capabilities and increasing the impact of data-destructive attacks such as ransomware.

Recommendation

Deploy the Sigma detection rule below to monitor for suspicious DLL loads and tune the filter list against your environment's known backup and administrative software inventory to reduce false positives.

• Enable Sysmon image load logging (Event ID 7) to collect the necessary telemetry.
• Establish a baseline of legitimate applications that load vsstrace.dll in your environment to replace the generic 'Program Files' filters.