Suspicious APT29 Zulip C2 Communication via curl 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
- T1102Web Service
Exfiltration
Impact

What it detects

This rule detects requests to the Zulip chat messages API using a curl User-Agent, the abuse of a legitimate collaboration service for command-and-control in the APT29 German Embassy campaign. The actor posted to the api v1 messages endpoint via curl to blend with normal SaaS traffic. Because Zulip is legitimate, the curl agent and messages path together narrow the match.

Reporting behind it

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Suspicious APT29 Zulip C2 Communication via curl 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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