Suspicious Cobalt Strike Loader C2 Traffic via Forged MSIE yie9 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 command-and-control traffic using the forged Internet Explorer 9 user-agent carrying the yie9 token observed with the Cobalt Strike PowerShell loader across Chinese and Russian infrastructure. Adversaries leverage a spoofed legacy browser user-agent to blend beacon traffic into normal web requests.

Reporting behind it

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Suspicious Cobalt Strike Loader C2 Traffic via Forged MSIE yie9 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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