Suspicious .NET Code Compilation

 1[metadata]
 2creation_date = "2020/08/21"
 3integration = ["endpoint", "windows"]
 4maturity = "production"
 5updated_date = "2024/08/07"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10Identifies executions of .NET compilers with suspicious parent processes, which can indicate an attacker's attempt to
11compile code after delivery in order to bypass security mechanisms.
12"""
13from = "now-9m"
14index = [
15    "winlogbeat-*",
16    "logs-endpoint.events.process-*",
17    "logs-windows.*",
18    "endgame-*",
19    "logs-system.security*",
20]
21language = "eql"
22license = "Elastic License v2"
23name = "Suspicious .NET Code Compilation"
24risk_score = 47
25rule_id = "201200f1-a99b-43fb-88ed-f65a45c4972c"
26setup = """## Setup
27
28If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
29events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
30Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
31`event.ingested` to @timestamp.
32For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
33"""
34severity = "medium"
35tags = [
36    "Domain: Endpoint",
37    "OS: Windows",
38    "Use Case: Threat Detection",
39    "Tactic: Defense Evasion",
40    "Tactic: Execution",
41    "Data Source: Elastic Endgame",
42    "Data Source: Elastic Defend",
43    "Data Source: System",
44]
45timestamp_override = "event.ingested"
46type = "eql"
47
48query = '''
49process where host.os.type == "windows" and event.type == "start" and
50  process.name : ("csc.exe", "vbc.exe") and
51  process.parent.name : ("wscript.exe", "mshta.exe", "cscript.exe", "wmic.exe", "svchost.exe", "rundll32.exe", "cmstp.exe", "regsvr32.exe")
52'''
53
54
55[[rule.threat]]
56framework = "MITRE ATT&CK"
57[[rule.threat.technique]]
58id = "T1027"
59name = "Obfuscated Files or Information"
60reference = "https://attack.mitre.org/techniques/T1027/"
61[[rule.threat.technique.subtechnique]]
62id = "T1027.004"
63name = "Compile After Delivery"
64reference = "https://attack.mitre.org/techniques/T1027/004/"
65
66
67
68[rule.threat.tactic]
69id = "TA0005"
70name = "Defense Evasion"
71reference = "https://attack.mitre.org/tactics/TA0005/"
72[[rule.threat]]
73framework = "MITRE ATT&CK"
74[[rule.threat.technique]]
75id = "T1059"
76name = "Command and Scripting Interpreter"
77reference = "https://attack.mitre.org/techniques/T1059/"
78[[rule.threat.technique.subtechnique]]
79id = "T1059.005"
80name = "Visual Basic"
81reference = "https://attack.mitre.org/techniques/T1059/005/"
82
83
84
85[rule.threat.tactic]
86id = "TA0002"
87name = "Execution"
88reference = "https://attack.mitre.org/tactics/TA0002/"