User Added to Local Administrators Group

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects addition of users to the local administrator group via "Net" or "Add-LocalGroupMember".

Known false positives

Administrative activity

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1098` Account Manipulation
Privilege Escalation	`T1098` Account Manipulation

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: User Added to Local Administrators Group
id: ad720b90-25ad-43ff-9b5e-5c841facc8e5
related:
    - id: ffa28e60-bdb1-46e0-9f82-05f7a61cc06e # Remote Desktop groups
      type: similar
    - id: 10fb649c-3600-4d37-b1e6-56ea90bb7e09 # Privileged groups
      type: similar
status: test
description: Detects addition of users to the local administrator group via "Net" or "Add-LocalGroupMember".
references:
    - https://blog.talosintelligence.com/2022/08/recent-cyber-attack.html?m=1
author: Florian Roth (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)
date: 2022-08-12
modified: 2023-03-02
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1098
logsource:
    category: process_creation
    product: windows
detection:
    selection_main:
        - CommandLine|contains|all:
              # net.exe
              - 'localgroup '
              - ' /add'
        - CommandLine|contains|all:
              # powershell.exe
              - 'Add-LocalGroupMember '
              - ' -Group '
    selection_group:
        CommandLine|contains:
            - ' administrators '
            - ' administrateur' # Typo without an 'S' so we catch both
    condition: all of selection_*
falsepositives:
    - Administrative activity
level: medium

Stages and Predicates

Stage 0: `condition`

all of selection_*

Stage 1: `selection_main`

selection_main:
    - CommandLine|contains|all:
          - 'localgroup '
          - ' /add'
    - CommandLine|contains|all:
          - 'Add-LocalGroupMember '
          - ' -Group '

Stage 2: `selection_group`

selection_group:
    CommandLine|contains:
        - ' administrators '
        - ' administrateur'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-Group` corpus 3 (sigma 3) `/add` corpus 4 (sigma 4) `administrateur` corpus 3 (sigma 3) `administrators` corpus 2 (sigma 2) `Add-LocalGroupMember` corpus 3 (sigma 3) `localgroup` corpus 3 (sigma 3)	`field:"CommandLine" kind:match`

User Added to Local Administrators Group

Known false positives

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection_main

Stage 2: selection_group

Indicators

Stage 0: `condition`

Stage 1: `selection_main`

Stage 2: `selection_group`