Proxy logs: suspicious exploit framework User-Agent strings

ATT&CK techniques

C2

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
- T1071.001Web Protocols
Exfiltration
Impact

What it detects

This rule flags proxy traffic where the User-Agent header matches specific patterns commonly used by exploit and pentest frameworks (for example, Metasploit- and Cobalt Strike-associated strings), as well as generic exploit-related markers. Such traffic matters because unusual or highly patterned User-Agent values can indicate automated tooling used for command-and-control, reconnaissance, or exploitation. It relies on proxy log telemetry containing a client User-Agent field and compares it against a defined set of suspicious string matches.

Reporting behind it

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Proxy logs: suspicious exploit framework User-Agent strings

Pivot detection · T1071.001 · 9 related

Changelog

v2

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.

suspicious-exploit-framework-user-agent-strings-in-proxy-logs-fdd1bfb5

title: "Proxy logs: suspicious exploit framework User-Agent strings"
id: 6c608955-ae1f-407e-ac1d-aaab6a356f2b
status: test
description: This rule flags proxy traffic where the User-Agent header matches specific patterns commonly used by exploit and pentest frameworks (for example, Metasploit- and Cobalt Strike-associated strings), as well as generic exploit-related markers. Such traffic matters because unusual or highly patterned User-Agent values can indicate automated tooling used for command-and-control, reconnaissance, or exploitation. It relies on proxy log telemetry containing a client User-Agent field and compares it against a defined set of suspicious string matches.
references:
  - https://blog.didierstevens.com/2015/03/16/quickpost-metasploit-user-agent-strings/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/web/proxy_generic/proxy_ua_frameworks.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2017-07-08
modified: 2025-01-18
tags:
  - attack.command-and-control
  - attack.t1071.001
logsource:
  category: proxy
detection:
  selection:
    c-useragent:
      - Internet Explorer *
      - Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; InfoPath.2)
      - Mozilla/4.0 (compatible; Metasploit RSPEC)
      - Mozilla/4.0 (compatible; MSIE 6.1; Windows NT)
      - Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1)
      - Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)
      - Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0)
      - Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; Trident/4.0; SIMBAR={7DB0F6DE-8DE7-4841-9084-28FA914B0F2E}; SLCC1; .N
      - Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)
      - Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/525.13 (KHTML, like Gecko) Chrome/4.0.221.6 Safari/525.13
      - Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64; Trident/5.0; MAAU)
      - Mozilla/5.0
      - Mozilla/4.0 (compatible; SPIPE/1.0
      - Mozilla/5.0 (Windows NT 6.3; rv:39.0) Gecko/20100101 Firefox/35.0
      - Sametime Community Agent
      - X-FORWARDED-FOR
      - DotDotPwn v2.1
      - SIPDROID
      - Mozilla/5.0 (Windows NT 10.0; Win32; x32; rv:60.0)
      - Mozilla/6.0 (X11; Linux x86_64; rv:24.0) Gecko/20140205     Firefox/27.0 Iceweasel/25.3.0
      - "*wordpress hash grabber*"
      - "*exploit*"
      - Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36
  condition: selection
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: fdd1bfb5-f60b-4a35-910e-f36ed3d0b32f
    type: derived

Convert

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