Malicious CastleLoader C2 Communication via Hardcoded User-Agent

ATT&CK techniques

C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071.001Web Protocols
Exfiltration
Impact

What it detects

This rule detects outbound HTTP requests using the hardcoded non-standard User-Agent token associated with CastleLoader C2 check-ins. The loader beacons to its server with this fixed string before receiving tasks.

Reporting behind it

Related detections9 linkedT1071.001 — drag to rearrange

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Malicious CastleLoader C2 Communication via Hardcoded User-Agent

Pivot detection · T1071.001 · 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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