SilentMare Loader C2 Beacon via Custom GatewayClient User-Agent (via proxy)

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 carrying the hardcoded GatewayClient and Metrics User-Agent strings used by the SilentMare and HollowMare trojan families distributed through Google Search ads. These custom agents identify updater check-ins that pull AES-encrypted .NET payloads from attacker infrastructure, making them a reliable network fingerprint for the loader stage.

Reporting behind it

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SilentMare Loader C2 Beacon via Custom GatewayClient User-Agent (via proxy)

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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