TCC Bypass via Mounted APFS Snapshot Access

Elastic Stack Serverless Security

Identifies the use of the mount_apfs command to mount the entire file system through Apple File System (APFS) snapshots as read-only and with the noowners flag set. This action enables the adversary to access almost any file in the file system, including all user data and files protected by Apple’s privacy framework (TCC).

Rule type: query

Rule indices:

auditbeat-*
logs-endpoint.events.*

Severity: high

Risk score: 73

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://theevilbit.github.io/posts/cve_2020_9771/

Tags:

Elastic
Host
macOS
Threat Detection
Defense Evasion
CVE_2020_9771

Version: 3

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

		event.category : process and event.type : (start or process_started) and process.name : mount_apfs and
  process.args : (/System/Volumes/Data and noowners)

Framework: MITRE ATT&CKTM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Direct Volume Access
- ID: T1006
- Reference URL: https://attack.mitre.org/techniques/T1006/