Microsoft 365 Exchange Malware Filter Policy Deletion

 1[metadata]
 2creation_date = "2020/11/19"
 3integration = ["o365"]
 4maturity = "production"
 5updated_date = "2024/05/21"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10Identifies when a malware filter policy has been deleted in Microsoft 365. A malware filter policy is used to alert
11administrators that an internal user sent a message that contained malware. This may indicate an account or machine
12compromise that would need to be investigated. Deletion of a malware filter policy may be done to evade detection.
13"""
14false_positives = [
15    """
16    A malware filter policy may be deleted by a system or network administrator. Verify that the configuration change
17    was expected. Exceptions can be added to this rule to filter expected behavior.
18    """,
19]
20from = "now-30m"
21index = ["filebeat-*", "logs-o365*"]
22language = "kuery"
23license = "Elastic License v2"
24name = "Microsoft 365 Exchange Malware Filter Policy Deletion"
25note = """## Setup
26
27The Office 365 Logs Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule."""
28references = [
29    "https://docs.microsoft.com/en-us/powershell/module/exchange/remove-malwarefilterpolicy?view=exchange-ps",
30]
31risk_score = 47
32rule_id = "d743ff2a-203e-4a46-a3e3-40512cfe8fbb"
33severity = "medium"
34tags = [
35    "Domain: Cloud",
36    "Data Source: Microsoft 365",
37    "Use Case: Configuration Audit",
38    "Tactic: Defense Evasion",
39]
40timestamp_override = "event.ingested"
41type = "query"
42
43query = '''
44event.dataset:o365.audit and event.provider:Exchange and event.category:web and event.action:"Remove-MalwareFilterPolicy" and event.outcome:success
45'''
46
47
48[[rule.threat]]
49framework = "MITRE ATT&CK"
50[[rule.threat.technique]]
51id = "T1562"
52name = "Impair Defenses"
53reference = "https://attack.mitre.org/techniques/T1562/"
54
55
56[rule.threat.tactic]
57id = "TA0005"
58name = "Defense Evasion"
59reference = "https://attack.mitre.org/tactics/TA0005/"