Sigma rule: Antivirus - Web Shell Detection Signature

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-a88f155037e7, updated 2026-06-29T00:00:00.000Z.

Rule

Title
Antivirus - Web Shell Detection Signature
Status
test
Level
high
Author
Florian Roth (Nextron Systems), Arnim Rupp
Date
2018-09-09
Modified
2026-06-29
File
rules/category/antivirus/av_webshell.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects a highly relevant Antivirus alert that reports a web shell.
It's highly recommended to tune this rule to the specific strings used by your anti virus solution by downloading a big WebShell repository from e.g. github and checking the matches.
This event must not be ignored just because the AV has blocked the malware but investigate, how it came there in the first place.

Log source

category
antivirus

Detection

selection:
    - Signature|startswith:
          - 'ASP.'
          - 'IIS/BackDoor'
          - 'JAVA/Backdoor'
          - 'JSP.'
          - 'Perl.'
          - 'PHP.'
          - 'Troj/ASP'
          - 'Troj/JSP'
          - 'Troj/PHP'
          - 'VBS/Uxor' # looking for 'VBS/' would also find downloader's and droppers meant for desktops
    - Signature|contains:
          - 'ASP_' # looking for 'VBS_' would also find downloader's and droppers meant for desktops
          - 'ASP:'
          - 'ASP.Agent'
          - 'ASP/'
          # - 'ASP/Agent'
          - 'Aspdoor'
          - 'ASPXSpy'
          - 'Backdoor.ASP'
          - 'Backdoor.Java'
          - 'Backdoor.JSP'
          - 'Backdoor.PHP'
          - 'Backdoor.VBS'
          - 'Backdoor/ASP'
          - 'Backdoor/Java'
          - 'Backdoor/JSP'
          - 'Backdoor/PHP'
          - 'Backdoor/VBS'
          - 'C99shell'
          - 'Chopper'
          - 'filebrowser'
          - 'JSP_'
          - 'JSP:'
          - 'JSP.Agent'
          - 'JSP/'
          # - 'JSP/Agent'
          - 'Perl:'
          - 'Perl/'
          - 'PHP_'
          - 'PHP:'
          - 'PHP.Agent'
          - 'PHP/'
          # - 'PHP/Agent'
          - 'PHPShell'
          - 'PShlSpy'
          - 'SinoChoper'
          - 'Trojan.ASP'
          - 'Trojan.JSP'
          - 'Trojan.PHP'
          - 'Trojan.VBS'
          - 'VBS.Agent'
          - 'VBS/Agent'
          - 'Webshell'
condition: selection

False positives (as the rule lists them)

  • Unlikely

Tags

  • attack.persistence
  • attack.t1505.003

MITRE ATT&CK ids this rule names

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/category/antivirus/av_webshell.yml

Sources and licences

  • SigmaHQ

    "Antivirus - Web Shell Detection Signature" by Florian Roth (Nextron Systems), Arnim Rupp (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/category/antivirus/av_webshell.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: Antivirus - Web Shell Detection Signature",
entity page, dataset version ref-a88f155037e7, updated 2026-06-29T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/fdf135a2-9241-4f96-a114-bb404948f736 (accessed 2026-11-03).
Underlying source: SigmaHQ rule fdf135a2-9241-4f96-a114-bb404948f736, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.