macOS: Time Machine Exclusion Added via tmutil addexclusion

Alerts on tmutil commands that add new Time Machine exclusions to skip backing up selected files.

FreeReviewedSigma · Medium · v2

Product: macos
Category: process_creation
Author: Pratinav Chandra (SigmaHQ), DRL 1.1
Published: 2024-05-29
Updated: 2026-07-31

ATT&CK techniques

Impact

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
- T1490Inhibit System Recovery

What it detects

This rule flags process executions of tmutil on macOS where a Time Machine exclusion is being added using the addexclusion argument. Attackers may use this to prevent specific files or paths from being included in backups, reducing the likelihood of recovery and forensic visibility. Detection relies on process creation telemetry, matching the tmutil binary and the presence of the addexclusion command-line string.

Reporting behind it

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Malicious Inhibit System Recovery via Shadow Copy and Boot Config Tampering (via process_creation)

Malicious Recovery Disablement via Bcdedit RecoveryEnabled No

Suspicious Volume Shadow Copy Deletion via vssadmin or wmic

macOS: Time Machine Exclusion Added via tmutil addexclusion

Pivot detection · T1490 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

macos-detect-tmutil-adding-time-machine-exclusions-addexclusion-9acf45ed

title: "macOS: Time Machine Exclusion Added via tmutil addexclusion"
id: a1e1e488-6e24-4b0d-a38a-08b789d2af75
status: test
description: This rule flags process executions of tmutil on macOS where a Time Machine exclusion is being added using the addexclusion argument. Attackers may use this to prevent specific files or paths from being included in backups, reducing the likelihood of recovery and forensic visibility. Detection relies on process creation telemetry, matching the tmutil binary and the presence of the addexclusion command-line string.
references:
  - https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1490/T1490.md#atomic-test-12---disable-time-machine
  - https://www.loobins.io/binaries/tmutil/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/macos/process_creation/proc_creation_macos_tmutil_exclude_file_from_backup.yml
author: Pratinav Chandra, Huntrule Team
date: 2024-05-29
tags:
  - attack.impact
  - attack.t1490
logsource:
  category: process_creation
  product: macos
detection:
  selection_img:
    - Image|endswith: /tmutil
    - CommandLine|contains: tmutil
  selection_cmd:
    CommandLine|contains: addexclusion
  condition: all of selection_*
falsepositives:
  - Legitimate administrator activity
level: medium
license: DRL-1.1
related:
  - id: 9acf45ed-3a26-4062-bf08-56857613eb52
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

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