New or Renamed User Account with '$' Character

testmedium

log source: windows · securityauthor Ilyas Ochkov, oscd.communitydate 2019-10-25

description

What this is, in brief.

Detects the creation of a user with the "$" character. This can be used by attackers to hide a user or trick detection systems that lack the parsing mechanisms.

rule source (YAML)

title: New or Renamed User Account with '$' Character
id: cfeed607-6aa4-4bbd-9627-b637deb723c8
status: test
description: |
    Detects the creation of a user with the "$" character. This can be used by attackers to hide a user or trick detection systems that lack the parsing mechanisms.
references:
    - https://twitter.com/SBousseaden/status/1387743867663958021
author: Ilyas Ochkov, oscd.community
date: 2019-10-25
modified: 2024-01-16
tags:
    - attack.stealth
    - attack.t1036
logsource:
    product: windows
    service: security
detection:
    selection_create:
        EventID: 4720 # create user
        SamAccountName|contains: '$'
    selection_rename:
        EventID: 4781 # rename user
        NewTargetUserName|contains: '$'
    filter_main_homegroup:
        EventID: 4720
        TargetUserName: 'HomeGroupUser$'
    condition: 1 of selection_* and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium

detects techniques (1)

ATT&CK techniques this enables or maps to.

T1036Masquerading

references

External citations — patches, advisories, analysis.

https://twitter.com/SBousseaden/status/1387743867663958021