Linux Setgid Capability Set on a Binary via Setcap Utility

Status: experimental
Severity: low
Log source: category process_creation, product linux
Author: Luc Génaux
Source: github.com/SigmaHQ/sigma

Detects the use of the 'setcap' utility to set the 'setgid' capability (cap_setgid) on a binary file. This capability allows a non privileged process to make arbitrary manipulations of group IDs (GIDs), including setting its current GID to a value that would otherwise be restricted (i.e. GID 0, the root group). This behavior can be used by adversaries to backdoor a binary in order to escalate privileges again in the future if needed.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1554` Compromise Host Software Binary
Privilege Escalation	`T1548` Abuse Elevation Control Mechanism

Telemetry coverage

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

Rule body

title: Linux Setgid Capability Set on a Binary via Setcap Utility
id: 3a716279-c18c-4488-83be-f9ececbfb9fc
status: experimental
description: |
    Detects the use of the 'setcap' utility to set the 'setgid' capability (cap_setgid) on a binary file.
    This capability allows a non privileged process to make arbitrary manipulations of group IDs (GIDs), including setting its current GID to a value that would otherwise be restricted (i.e. GID 0, the root group).
    This behavior can be used by adversaries to backdoor a binary in order to escalate privileges again in the future if needed.
references:
    - https://man7.org/linux/man-pages/man8/setcap.8.html
    - https://dfir.ch/posts/linux_capabilities/
    - https://juggernaut-sec.com/capabilities/#cap_setgid
author: Luc Génaux
date: 2026-01-24
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1548
    - attack.t1554
logsource:
    product: linux
    category: process_creation
detection:
    selection:
        Image|endswith: '/setcap'
        CommandLine|contains: 'cap_setgid'
    condition: selection
falsepositives:
    - Unknown
level: low

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: '/setcap'
    CommandLine|contains: 'cap_setgid'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`cap_setgid`	`field:"CommandLine" kind:match value:"cap_setgid"`
`Image`	ends_with	`/setcap`	`field:"Image" kind:ends_with value:"/setcap"`