SigmaHQ/rules/proxy/proxy_empty_ua.yml

title: Empty User Agent
status: experimental
description: Detects suspicious empty user agent strings in proxy logs
references:
    - https://twitter.com/Carlos_Perez/status/883455096645931008
author: Florian Roth
logsource:
    category: proxy
detection:
    selection:
      # Empty string - as used by Powershell's (New-Object Net.WebClient).DownloadString 
      UserAgent: ''
    condition: selection
fields:
    - ClientIP
    - URL
    - UserAgent
falsepositives:
    - Unknown
level: medium
User-Agent Rules 2017-07-08 14:37:44 +00:00			`title: Empty User Agent`
			`status: experimental`
			`description: Detects suspicious empty user agent strings in proxy logs`
Change "reference" to "references" to match new schema 2018-01-27 23:12:19 +00:00			`references:`
User-Agent Rules 2017-07-08 14:37:44 +00:00			`- https://twitter.com/Carlos_Perez/status/883455096645931008`
			`author: Florian Roth`
			`logsource:`
Fixed rules * Replaced unspecified logsource attribute 'type' with 'category' * Usage of service 'auth' for linux logs 2017-09-10 22:35:52 +00:00			`category: proxy`
User-Agent Rules 2017-07-08 14:37:44 +00:00			`detection:`
			`selection:`
Simplified rule 2018-11-21 21:34:04 +00:00			`# Empty string - as used by Powershell's (New-Object Net.WebClient).DownloadString`
			`UserAgent: ''`
User-Agent Rules 2017-07-08 14:37:44 +00:00			`condition: selection`
Added field names to first rules 2017-09-12 21:54:04 +00:00			`fields:`
			`- ClientIP`
			`- URL`
			`- UserAgent`
User-Agent Rules 2017-07-08 14:37:44 +00:00			`falsepositives:`
			`- Unknown`
			`level: medium`