huntrule

Webserver: OWASSRF exploitation attempt via OWA to PowerShell backend

Flags webserver POSTs returning 200 that request both /owa/mastermailbox and /powershell, consistent with OWASSRF exploitation attempts.

FreeReviewedSigma · Critical · v5
Category
webserver
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 webserver activity that matches a successful HTTP POST (status 200) to OWA endpoints containing both /owa/mastermailbox and /powershell, with a specific browser-like User-Agent and request pattern. Such traffic is consistent with OWASSRF-style attempts to reach a PowerShell backend through public OWA paths. Telemetry relies on webserver HTTP request fields including User-Agent, method, status, and the requested URI query.

Reporting behind it

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Possible Marimo Unauthenticated Terminal WebSocket Access via Web Request (via webserver)
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Webserver: OWASSRF 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.