Suspicious .NET Code Compilation

 1[metadata]
 2creation_date = "2020/08/21"
 3integration = ["endpoint", "windows", "system", "m365_defender", "sentinel_one_cloud_funnel", "crowdstrike"]
 4maturity = "production"
 5updated_date = "2024/10/31"
 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    "logs-crowdstrike.fdr*",
26]
27language = "eql"
28license = "Elastic License v2"
29name = "Suspicious .NET Code Compilation"
30risk_score = 47
31rule_id = "201200f1-a99b-43fb-88ed-f65a45c4972c"
32severity = "medium"
33tags = [
34    "Domain: Endpoint",
35    "OS: Windows",
36    "Use Case: Threat Detection",
37    "Tactic: Defense Evasion",
38    "Tactic: Execution",
39    "Data Source: Elastic Endgame",
40    "Data Source: Elastic Defend",
41    "Data Source: System",
42    "Data Source: Microsoft Defender for Endpoint",
43    "Data Source: Sysmon",
44    "Data Source: SentinelOne",
45    "Data Source: Crowdstrike",
46]
47timestamp_override = "event.ingested"
48type = "eql"
49
50query = '''
51process where host.os.type == "windows" and event.type == "start" and
52  process.name : ("csc.exe", "vbc.exe") and
53  process.parent.name : ("wscript.exe", "mshta.exe", "cscript.exe", "wmic.exe", "svchost.exe", "rundll32.exe", "cmstp.exe", "regsvr32.exe")
54'''
55
56
57[[rule.threat]]
58framework = "MITRE ATT&CK"
59[[rule.threat.technique]]
60id = "T1027"
61name = "Obfuscated Files or Information"
62reference = "https://attack.mitre.org/techniques/T1027/"
63[[rule.threat.technique.subtechnique]]
64id = "T1027.004"
65name = "Compile After Delivery"
66reference = "https://attack.mitre.org/techniques/T1027/004/"
67
68
69
70[rule.threat.tactic]
71id = "TA0005"
72name = "Defense Evasion"
73reference = "https://attack.mitre.org/tactics/TA0005/"
74[[rule.threat]]
75framework = "MITRE ATT&CK"
76[[rule.threat.technique]]
77id = "T1059"
78name = "Command and Scripting Interpreter"
79reference = "https://attack.mitre.org/techniques/T1059/"
80[[rule.threat.technique.subtechnique]]
81id = "T1059.005"
82name = "Visual Basic"
83reference = "https://attack.mitre.org/techniques/T1059/005/"
84
85
86
87[rule.threat.tactic]
88id = "TA0002"
89name = "Execution"
90reference = "https://attack.mitre.org/tactics/TA0002/"