Possible SMB Share C2 Beacon via Lock File Polling

ATT&CK techniques

C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071Application Layer Protocol
Exfiltration
Impact

What it detects

This rule detects repeated access to lock extension files on a network share which matches the C3 UNC file share command and control channel described in the WithSecure lab where randomized lock files were written and polled on a roughly ten second interval. Command and control routed over an internal SMB share evades outbound network controls so lock file access patterns on shares are worth surfacing for triage.

Reporting behind it

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Possible SMB Share C2 Beacon via Lock File Polling

Pivot detection · T1071 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

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