rules/proxy/proxy_empty_ua.yml

title: Empty User Agent
id: 21e44d78-95e7-421b-a464-ffd8395659c4
status: test
description: Detects suspicious empty user agent strings in proxy logs
author: Florian Roth
references:
  - https://twitter.com/Carlos_Perez/status/883455096645931008
date: 2017/07/08
modified: 2021/11/27
logsource:
  category: proxy
detection:
  selection:
      # Empty string - as used by Powershell's (New-Object Net.WebClient).DownloadString
    c-useragent: ''
  condition: selection
fields:
  - ClientIP
  - c-uri
  - c-useragent
falsepositives:
  - Unknown
level: medium
tags:
  - attack.defense_evasion
  - attack.command_and_control
  - attack.t1071.001
User-Agent Rules 2017-07-08 08:37:44 -06:00			`title: Empty User Agent`
Added UUIDs to rules 2019-11-12 23:12:27 +01:00			`id: 21e44d78-95e7-421b-a464-ffd8395659c4`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`status: test`
User-Agent Rules 2017-07-08 08:37:44 -06:00			`description: Detects suspicious empty user agent strings in proxy logs`
			`author: Florian Roth`
Second round 2020-09-15 07:02:30 -06:00			`references:`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`- https://twitter.com/Carlos_Perez/status/883455096645931008`
			`date: 2017/07/08`
			`modified: 2021/11/27`
User-Agent Rules 2017-07-08 08:37:44 -06:00			`logsource:`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`category: proxy`
User-Agent Rules 2017-07-08 08:37:44 -06:00			`detection:`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`selection:`
fix: fixed missing date fields in proxy rules 2020-01-30 15:20:52 +01:00			`# Empty string - as used by Powershell's (New-Object Net.WebClient).DownloadString`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`c-useragent: ''`
			`condition: selection`
Added field names to first rules 2017-09-12 23:54:04 +02:00			`fields:`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`- ClientIP`
			`- c-uri`
			`- c-useragent`
User-Agent Rules 2017-07-08 08:37:44 -06:00			`falsepositives:`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`- Unknown`
User-Agent Rules 2017-07-08 08:37:44 -06:00			`level: medium`
Second round 2020-09-15 07:02:30 -06:00			`tags:`
			`- attack.defense_evasion`
			`- attack.command_and_control`
$frack113$ Change status for old rules 2021-11-27 11:33:14 +01:00			`- attack.t1071.001`