Detection rules › Sigma

Hidden Local User Creation

Status
test
Severity
high
Log source
product windows, service security
Author
Christian Burkard (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects the creation of a local hidden user account which should not happen for event ID 4720.

MITRE ATT&CK coverage

TacticTechniques
Persistence

Telemetry coverage

Rule body

title: Hidden Local User Creation
id: 7b449a5e-1db5-4dd0-a2dc-4e3a67282538
status: test
description: Detects the creation of a local hidden user account which should not happen for event ID 4720.
references:
    - https://twitter.com/SBousseaden/status/1387743867663958021
author: Christian Burkard (Nextron Systems)
date: 2021-05-03
modified: 2024-01-16
tags:
    - attack.persistence
    - attack.t1136.001
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4720
        TargetUserName|endswith: '$'
    filter_main_homegroup:
        TargetUserName: 'HomeGroupUser$'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_*

Stage 1: selection

selection:
    EventID: 4720
    TargetUserName|endswith: '$'

Stage 2: not filter_main_homegroup

filter_main_homegroup:
    TargetUserName: 'HomeGroupUser$'

Exclusions

The rule actively suppresses these predicates.

FieldKindExcluded valuesSearch
TargetUserNameeqHomeGroupUser$excludes:TargetUserName field:"TargetUserName" value:"HomeGroupUser$"

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
TargetUserNameends_with
  • $ corpus 11 (sigma 7, splunk 2, kusto 2)
field:"TargetUserName" kind:ends_with value:"$"