User Has Been Deleted Via Userdel

Status: test
Severity: medium
Log source: category process_creation, product linux
Author: Tuan Le (NCSGroup)
Source: github.com/SigmaHQ/sigma

Detects execution of the "userdel" binary. Which is used to delete a user account and related files. This is sometimes abused by threat actors in order to cover their tracks

Known false positives

Legitimate administrator activities

MITRE ATT&CK coverage

Tactic	Techniques
Impact	`T1531` Account Access Removal

Telemetry coverage

Platform	Record / event type
Linux	Event ID 1: Process Create

Rule body

title: User Has Been Deleted Via Userdel
id: 08f26069-6f80-474b-8d1f-d971c6fedea0
status: test
description: Detects execution of the "userdel" binary. Which is used to delete a user account and related files. This is sometimes abused by threat actors in order to cover their tracks
references:
    - https://linuxize.com/post/how-to-delete-group-in-linux/
    - https://www.cyberciti.biz/faq/linux-remove-user-command/
    - https://www.cybrary.it/blog/0p3n/linux-commands-used-attackers/
    - https://linux.die.net/man/8/userdel
author: Tuan Le (NCSGroup)
date: 2022-12-26
tags:
    - attack.impact
    - attack.t1531
logsource:
    product: linux
    category: process_creation
detection:
    selection:
        Image|endswith: '/userdel'
    condition: selection
falsepositives:
    - Legitimate administrator activities
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '/userdel'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`/userdel`	`field:"Image" kind:ends_with value:"/userdel"`