huntrule

Antivirus Web Shell Signature Matches Across ASP, JSP, PHP, Perl, and VBS

Alerts on AV signatures indicating web shells/backdoors (ASP/JSP/PHP/Perl/VBS/Webshell) to support fast investigation of persistence.

FreeReviewedSigma · High · v5
Category
antivirus
Author
Florian Roth (Nextron Systems), Arnim Rupp (SigmaHQ), DRL 1.1
Published
2018-09-09
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 antivirus detections whose signature starts with common web-shell-related families (ASP, JSP, PHP, Perl, and VBS) or contains multiple web shell and backdoor filename patterns. Web shells enable persistent remote execution via a compromised web application, making these alerts high value even when the AV blocks the payload. Telemetry relies on antivirus alert metadata, specifically the reported signature text in the AV event.

Reporting behind it

Related detections9 linkedT1505.003 — drag to rearrange
Suspicious Weaver Ant In-Memory Web Shell Marker in Web Request (via webserver)
Malicious Web Server Process Spawning Command Interpreter via Web Shell (via process_creation)
Malicious Web Shell Written to SharePoint LAYOUTS Directory by Worker Process (via file_event)
Malicious IIS Worker Process Spawning Command Shell for Webshell Reconnaissance (via process_creation)
Malicious Command Shell Spawned by SQL Server via Process Creation (via process_creation)
Suspicious PHP Webshell Access with Hardcoded Key
Suspicious IIS Configuration Reconnaissance via Appcmd (via process_creation)
Malicious ManagementMailboxPicker Webshell Written by Diplomatic Specter
Malicious MOVEit human2 Webshell File Creation via file_event
Antivirus Web Shell Signature Matches Across ASP, JSP, PHP, Perl, and VBS
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.