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

Analysis Detection

ATT&CK techniques

Persistence

Recon
Resource Dev
Initial Access
Execution
Persistence
- T1505.003Web Shell
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
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

Possible Ivanti Connect Secure Webshell Access

Malicious Shell Spawned by SharePoint Worker Process w3wp

Suspicious SD-WAN Compromise JSP Webshell Access

Malicious AquaShell Webshell Access on Cisco Secure Email Gateway by UAT-9686

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

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

Pivot detection · T1505.003 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
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.

antivirus-web-shell-signature-alerts-asp-jsp-php-perl-vbs-and-related-backdoor-i-fdf135a2

title: Antivirus Web Shell Signature Matches Across ASP, JSP, PHP, Perl, and VBS
id: 5a4d83a1-ca1d-4527-9adf-f432844c8b46
status: test
description: 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.
references:
  - https://www.nextron-systems.com/?s=antivirus
  - https://github.com/tennc/webshell
  - https://www.virustotal.com/gui/file/bd1d52289203866645e556e2766a21d2275877fbafa056a76fe0cf884b7f8819/detection
  - https://www.virustotal.com/gui/file/308487ed28a3d9abc1fec7ebc812d4b5c07ab025037535421f64c60d3887a3e8/detection
  - https://www.virustotal.com/gui/file/7d3cb8a8ff28f82b07f382789247329ad2d7782a72dde9867941f13266310c80/detection
  - https://www.virustotal.com/gui/file/e841675a4b82250c75273ebf0861245f80c6a1c3d5803c2d995d9d3b18d5c4b5/detection
  - https://www.virustotal.com/gui/file/a80042c61a0372eaa0c2c1e831adf0d13ef09feaf71d1d20b216156269045801/detection
  - https://www.virustotal.com/gui/file/b219f7d3c26f8bad7e175934cd5eda4ddb5e3983503e94ff07d39c0666821b7e/detection
  - https://www.virustotal.com/gui/file/b8702acf32fd651af9f809ed42d15135f842788cd98d81a8e1b154ee2a2b76a2/detection
  - https://www.virustotal.com/gui/file/13ae8bfbc02254b389ab052aba5e1ba169b16a399d9bc4cb7414c4a73cd7dc78/detection
  - https://github.com/SigmaHQ/sigma/blob/master/rules/category/antivirus/av_webshell.yml
author: Florian Roth (Nextron Systems), Arnim Rupp, Huntrule Team
date: 2018-09-09
modified: 2026-06-29
tags:
  - attack.persistence
  - attack.t1505.003
logsource:
  category: antivirus
detection:
  selection:
    - Signature|startswith:
        - ASP.
        - IIS/BackDoor
        - JAVA/Backdoor
        - JSP.
        - Perl.
        - PHP.
        - Troj/ASP
        - Troj/JSP
        - Troj/PHP
        - VBS/Uxor
    - Signature|contains:
        - ASP_
        - "ASP:"
        - ASP.Agent
        - ASP/
        - 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/
        - "Perl:"
        - Perl/
        - PHP_
        - "PHP:"
        - PHP.Agent
        - PHP/
        - PHPShell
        - PShlSpy
        - SinoChoper
        - Trojan.ASP
        - Trojan.JSP
        - Trojan.PHP
        - Trojan.VBS
        - VBS.Agent
        - VBS/Agent
        - Webshell
  condition: selection
falsepositives:
  - Unlikely
level: high
license: DRL-1.1
related:
  - id: fdf135a2-9241-4f96-a114-bb404948f736
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

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