huntrule

Proxy logs: suspicious exploit framework User-Agent strings

High-severity match on proxy User-Agent strings commonly seen in exploit/pentest frameworks.

FreeReviewedSigma · High · v2
Category
proxy
Author
Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2017-07-08
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

C2

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags proxy traffic where the User-Agent header matches specific patterns commonly used by exploit and pentest frameworks (for example, Metasploit- and Cobalt Strike-associated strings), as well as generic exploit-related markers. Such traffic matters because unusual or highly patterned User-Agent values can indicate automated tooling used for command-and-control, reconnaissance, or exploitation. It relies on proxy log telemetry containing a client User-Agent field and compares it against a defined set of suspicious string matches.

Reporting behind it

Related detections9 linkedT1071.001 — drag to rearrange
Malicious axios NPM Supply Chain C2 Domain Resolution
Suspicious Reverse Shell via Dev TCP or Netcat
Malicious HarborWatch RAT Command and Control Beacon by User Agent (via proxy)
Suspicious UAT-10608 Credential Harvesting C2 Beacon via HTTP
Malicious BadIIS C2 Communication via lwxatisme User-Agent
Possible PS1Bot C2 Beacon With Drive Serial URI Pattern (via proxy)
Suspicious WarmCookie C2 Beacon With Fixed Firefox User-Agent
Malicious Renamed Python Interpreter Executing nvidia.py RAT
Malicious Self-Signed TLS Certificate With Exploit Subject via Zeek X509
Proxy logs: suspicious exploit framework User-Agent strings
Pivot detection · T1071.001 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. v1
    No changelog recorded for this version.2026-07-30

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