Suspicious .NET Code Compilation

 1[metadata]
 2creation_date = "2020/08/21"
 3integration = ["endpoint", "windows"]
 4maturity = "production"
 5updated_date = "2024/05/21"
 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]
44timestamp_override = "event.ingested"
45type = "eql"
46
47query = '''
48process where host.os.type == "windows" and event.type == "start" and
49  process.name : ("csc.exe", "vbc.exe") and
50  process.parent.name : ("wscript.exe", "mshta.exe", "cscript.exe", "wmic.exe", "svchost.exe", "rundll32.exe", "cmstp.exe", "regsvr32.exe")
51'''
52
53
54[[rule.threat]]
55framework = "MITRE ATT&CK"
56[[rule.threat.technique]]
57id = "T1027"
58name = "Obfuscated Files or Information"
59reference = "https://attack.mitre.org/techniques/T1027/"
60[[rule.threat.technique.subtechnique]]
61id = "T1027.004"
62name = "Compile After Delivery"
63reference = "https://attack.mitre.org/techniques/T1027/004/"
64
65
66
67[rule.threat.tactic]
68id = "TA0005"
69name = "Defense Evasion"
70reference = "https://attack.mitre.org/tactics/TA0005/"
71[[rule.threat]]
72framework = "MITRE ATT&CK"
73[[rule.threat.technique]]
74id = "T1059"
75name = "Command and Scripting Interpreter"
76reference = "https://attack.mitre.org/techniques/T1059/"
77[[rule.threat.technique.subtechnique]]
78id = "T1059.005"
79name = "Visual Basic"
80reference = "https://attack.mitre.org/techniques/T1059/005/"
81
82
83
84[rule.threat.tactic]
85id = "TA0002"
86name = "Execution"
87reference = "https://attack.mitre.org/tactics/TA0002/"