huntrule

Detects OWASSRF Proxy Exploitation Attempt via OWA to PowerShell Backend

Identifies proxy POSTs that return 200 and request both /owa/mastermailbox and /powershell, indicating potential OWASSRF exploitation.

FreeReviewedSigma · Critical · v5
Category
proxy
Author
Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2022-12-22
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Initial Access

  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 HTTP POST requests that use the OWA master mailbox path and target the /powershell backend in a way consistent with an OWASSRF exploitation attempt. It matters because attackers can leverage the proxy behavior of Exchange OWA to reach PowerShell endpoints. The detection relies on proxy telemetry fields such as client user agent, request method, response status, and the requested URI path segments.

Reporting behind it

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Detects OWASSRF Proxy Exploitation Attempt via OWA to PowerShell Backend
Pivot detection · T1190 · 9 related

Changelog

v5
  1. v5
    Candidate ingested via manual entry.2026-07-31
  2. v4
    Candidate ingested via manual entry.2026-07-31
  3. v3
    Candidate ingested via manual entry.2026-07-31
  4. v2
    Candidate ingested via manual entry.2026-07-31
  5. 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.