huntrule

Detect SolarWinds SUPERNOVA Webshell URL Access on Webservers (logoimagehandler.ashx)

Identifies webserver traffic consistent with SUPERNOVA webshell access targeting logoimagehandler.ashx with a clazz query parameter.

FreeReviewedSigma · Critical · v5
Category
webserver
Author
Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2020-12-17
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Persistence

  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 web requests whose URL query parameters reference the SUPERNOVA webshell pattern for "logoimagehandler.ashx" and include "clazz". Attackers may use this functionality to establish persistence or execute malicious activity through a webshell, making targeted URL access a high-value signal. It relies on webserver HTTP request telemetry, specifically the requested URI query string and, in one case, a 500 response status.

Reporting behind it

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Malicious IIS Worker Process Spawning Command Shell Reconnaissance
Malicious StyleSmuggler (CVE-2026-75650) Web Shell Dropped In Magento Product Image Cache (via file_event)
Suspicious Web Shell File Written to IIS wwwroot Directory
Possible Citrix ShareFile Unauthenticated Upload Path Traversal Webshell (CVE-2023-24489) (via webserver)
Possible Unauthenticated Admin Creation in Dynamicweb CVE-2022-25369
Detect SolarWinds SUPERNOVA Webshell URL Access on Webservers (logoimagehandler.ashx)
Pivot detection · T1505.003 · 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.