Suspicious .NET Code Compilation

 1[metadata]
 2creation_date = "2020/08/21"
 3integration = ["endpoint", "windows", "system", "m365_defender", "sentinel_one_cloud_funnel"]
 4maturity = "production"
 5updated_date = "2024/10/15"
 6min_stack_version = "8.14.0"
 7min_stack_comments = "Breaking change at 8.14.0 for the Windows Integration."
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Identifies executions of .NET compilers with suspicious parent processes, which can indicate an attacker's attempt to
13compile code after delivery in order to bypass security mechanisms.
14"""
15from = "now-9m"
16index = [
17    "winlogbeat-*",
18    "logs-endpoint.events.process-*",
19    "logs-windows.forwarded*",
20    "logs-windows.sysmon_operational-*",
21    "endgame-*",
22    "logs-system.security*",
23    "logs-m365_defender.event-*",
24    "logs-sentinel_one_cloud_funnel.*",
25]
26language = "eql"
27license = "Elastic License v2"
28name = "Suspicious .NET Code Compilation"
29risk_score = 47
30rule_id = "201200f1-a99b-43fb-88ed-f65a45c4972c"
31setup = """## Setup
32
33If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2,
34events will not define `event.ingested` and default fallback for EQL rules was not added until version 8.2.
35Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate
36`event.ingested` to @timestamp.
37For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html
38"""
39severity = "medium"
40tags = [
41    "Domain: Endpoint",
42    "OS: Windows",
43    "Use Case: Threat Detection",
44    "Tactic: Defense Evasion",
45    "Tactic: Execution",
46    "Data Source: Elastic Endgame",
47    "Data Source: Elastic Defend",
48    "Data Source: System",
49    "Data Source: Microsoft Defender for Endpoint",
50    "Data Source: Sysmon",
51    "Data Source: SentinelOne",
52]
53timestamp_override = "event.ingested"
54type = "eql"
55
56query = '''
57process where host.os.type == "windows" and event.type == "start" and
58  process.name : ("csc.exe", "vbc.exe") and
59  process.parent.name : ("wscript.exe", "mshta.exe", "cscript.exe", "wmic.exe", "svchost.exe", "rundll32.exe", "cmstp.exe", "regsvr32.exe")
60'''
61
62
63[[rule.threat]]
64framework = "MITRE ATT&CK"
65[[rule.threat.technique]]
66id = "T1027"
67name = "Obfuscated Files or Information"
68reference = "https://attack.mitre.org/techniques/T1027/"
69[[rule.threat.technique.subtechnique]]
70id = "T1027.004"
71name = "Compile After Delivery"
72reference = "https://attack.mitre.org/techniques/T1027/004/"
73
74
75
76[rule.threat.tactic]
77id = "TA0005"
78name = "Defense Evasion"
79reference = "https://attack.mitre.org/tactics/TA0005/"
80[[rule.threat]]
81framework = "MITRE ATT&CK"
82[[rule.threat.technique]]
83id = "T1059"
84name = "Command and Scripting Interpreter"
85reference = "https://attack.mitre.org/techniques/T1059/"
86[[rule.threat.technique.subtechnique]]
87id = "T1059.005"
88name = "Visual Basic"
89reference = "https://attack.mitre.org/techniques/T1059/005/"
90
91
92
93[rule.threat.tactic]
94id = "TA0002"
95name = "Execution"
96reference = "https://attack.mitre.org/tactics/TA0002/"