Suspicious Calendar File Modification

calendar Sep 5, 2023 · Domain: Endpoint OS: macOS Use Case: Threat Detection Tactic: Persistence Data Source: Elastic Defend  ·
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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.

Elastic rule (View on GitHub)

 1[metadata]
 2creation_date = "2021/01/19"
 3integration = ["endpoint"]
 4maturity = "production"
 5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
 6min_stack_version = "8.3.0"
 7updated_date = "2023/06/22"
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Identifies suspicious modifications of the calendar file by an unusual process. Adversaries may create a custom calendar
13notification procedure to execute a malicious program at a recurring interval to establish persistence.
14"""
15false_positives = ["Trusted applications for managing calendars and reminders."]
16from = "now-9m"
17index = ["logs-endpoint.events.*", "auditbeat-*"]
18language = "kuery"
19license = "Elastic License v2"
20name = "Suspicious Calendar File Modification"
21references = [
22    "https://labs.f-secure.com/blog/operationalising-calendar-alerts-persistence-on-macos",
23    "https://github.com/FSecureLABS/CalendarPersist",
24    "https://github.com/D00MFist/PersistentJXA/blob/master/CalendarPersist.js",
25]
26risk_score = 47
27rule_id = "cb71aa62-55c8-42f0-b0dd-afb0bb0b1f51"
28severity = "medium"
29tags = ["Domain: Endpoint", "OS: macOS", "Use Case: Threat Detection", "Tactic: Persistence", "Data Source: Elastic Defend"]
30timestamp_override = "event.ingested"
31type = "query"
32
33query = '''
34event.category:file and host.os.type:macos and event.action:modification and
35  file.path:/Users/*/Library/Calendars/*.calendar/Events/*.ics and
36  process.executable:
37  (* and not
38    (
39      /System/Library/* or
40      /System/Applications/Calendar.app/Contents/MacOS/* or
41      /System/Applications/Mail.app/Contents/MacOS/Mail or
42      /usr/libexec/xpcproxy or
43      /sbin/launchd or
44      /Applications/*
45    )
46  )
47'''
48
49
50[[rule.threat]]
51framework = "MITRE ATT&CK"
52[[rule.threat.technique]]
53id = "T1546"
54name = "Event Triggered Execution"
55reference = "https://attack.mitre.org/techniques/T1546/"
56
57
58[rule.threat.tactic]
59id = "TA0003"
60name = "Persistence"
61reference = "https://attack.mitre.org/tactics/TA0003/"

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