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Detection rules › Sigma

User Added to Local Administrator Group

Status
stable
Severity
medium
Log source
product windows, service security
Author
Florian Roth (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects the addition of a new member to the local administrator group, which could be legitimate activity or a sign of privilege escalation activity

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1078 Valid Accounts
PersistenceT1078 Valid Accounts, T1098 Account Manipulation
Privilege EscalationT1078 Valid Accounts, T1098 Account Manipulation
StealthT1078 Valid Accounts

Event coverage

ProviderEventTitle
Security-AuditingEvent ID 4732A member was added to a security-enabled local group.

Rule body yaml

title: User Added to Local Administrator Group
id: c265cf08-3f99-46c1-8d59-328247057d57
status: stable
description: Detects the addition of a new member to the local administrator group, which could be legitimate activity or a sign of privilege escalation activity
references:
    - https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-10/security/threat-protection/auditing/event-4732
    - https://learn.microsoft.com/en-us/windows-server/identity/ad-ds/manage/understand-security-identifiers
author: Florian Roth (Nextron Systems)
date: 2017-03-14
modified: 2021-01-17
tags:
    - attack.initial-access
    - attack.privilege-escalation
    - attack.stealth
    - attack.t1078
    - attack.persistence
    - attack.t1098
logsource:
    product: windows
    service: security
detection:
    selection_eid:
        EventID: 4732
    selection_group:
        - TargetUserName|startswith: 'Administr'
        - TargetSid: 'S-1-5-32-544'
    filter_main_computer_accounts:
        SubjectUserName|endswith: '$'
    condition: all of selection_* and not 1 of filter_*
falsepositives:
    - Legitimate administrative activity
level: medium

Stages and Predicates

Stage 0: condition

all of selection_* and not 1 of filter_*

Stage 1: selection_eid

selection_eid:
    EventID: 4732

Stage 2: selection_group

selection_group:
    - TargetUserName|startswith: 'Administr'
    - TargetSid: 'S-1-5-32-544'

Stage 3: not filter_main_computer_accounts

filter_main_computer_accounts:
    SubjectUserName|endswith: '$'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
SubjectUserNameends_with$

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
TargetSideq
  • S-1-5-32-544 corpus 3 (sigma 2, kusto 1)
TargetUserNamestarts_with
  • Administr corpus 2 (sigma 2)