Suspicious Calendar File Modification

Identifies suspicious modifications of the calendar file by an unusual process. Adversaries may create a custom calendar notification procedure to execute a malicious program at a recurring interval to establish persistence.

Rule type: query

Rule indices:

logs-endpoint.events.*
auditbeat-*

Severity: medium

Risk score: 47

Runs every: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Elastic
Host
macOS
Threat Detection
Persistence

Version: 1

Added (Elastic Stack release): 7.12.0

Rule authors: Elastic

Rule license: Elastic License v2

Potential false positives

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Trusted applications for managing calendars and reminders.

Rule query

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event.category:file and event.action:modification and
file.path:/Users/*/Library/Calendars/*.calendar/Events/*.ics and
process.executable: (* and not ( /System/Library/* or
/System/Applications/Calendar.app/Contents/MacOS/* or
/usr/libexec/xpcproxy or /sbin/launchd or
/Applications/* ) )

Threat mapping

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Framework: MITRE ATT&CK^TM

Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Event Triggered Execution
- ID: T1546
- Reference URL: https://attack.mitre.org/techniques/T1546/

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