Suspicious .NET Code Compilation

 1[metadata]
 2creation_date = "2020/08/21"
 3integration = ["endpoint", "windows"]
 4maturity = "production"
 5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
 6min_stack_version = "8.3.0"
 7updated_date = "2024/03/28"
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Identifies executions of .NET compilers with suspicious parent processes, which can indicate an attacker's attempt
13to compile code after delivery in order to bypass security mechanisms.
14"""
15from = "now-9m"
16index = ["winlogbeat-*", "logs-endpoint.events.process-*", "logs-windows.*", "endgame-*", "logs-system.security*"]
17language = "eql"
18license = "Elastic License v2"
19name = "Suspicious .NET Code Compilation"
20risk_score = 47
21rule_id = "201200f1-a99b-43fb-88ed-f65a45c4972c"
22setup = """## Setup
23
24If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
25events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
26Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
27`event.ingested` to @timestamp.
28For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
29"""
30severity = "medium"
31tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Defense Evasion", "Tactic: Execution", "Data Source: Elastic Endgame", "Data Source: Elastic Defend"]
32timestamp_override = "event.ingested"
33type = "eql"
34
35query = '''
36process where host.os.type == "windows" and event.type == "start" and
37  process.name : ("csc.exe", "vbc.exe") and
38  process.parent.name : ("wscript.exe", "mshta.exe", "cscript.exe", "wmic.exe", "svchost.exe", "rundll32.exe", "cmstp.exe", "regsvr32.exe")
39'''
40
41
42[[rule.threat]]
43framework = "MITRE ATT&CK"
44[[rule.threat.technique]]
45id = "T1027"
46name = "Obfuscated Files or Information"
47reference = "https://attack.mitre.org/techniques/T1027/"
48[[rule.threat.technique.subtechnique]]
49id = "T1027.004"
50name = "Compile After Delivery"
51reference = "https://attack.mitre.org/techniques/T1027/004/"
52
53
54
55[rule.threat.tactic]
56id = "TA0005"
57name = "Defense Evasion"
58reference = "https://attack.mitre.org/tactics/TA0005/"
59
60
61[[rule.threat]]
62framework = "MITRE ATT&CK"
63[[rule.threat.technique]]
64id = "T1059"
65name = "Command and Scripting Interpreter"
66reference = "https://attack.mitre.org/techniques/T1059/"
67[[rule.threat.technique.subtechnique]]
68id = "T1059.005"
69name = "Visual Basic"
70reference = "https://attack.mitre.org/techniques/T1059/005/"
71
72
73
74[rule.threat.tactic]
75id = "TA0002"
76name = "Execution"
77reference = "https://attack.mitre.org/tactics/TA0002/"