Execution via Windows Subsystem for Linux

 1[metadata]
 2creation_date = "2023/01/12"
 3integration = ["endpoint", "windows", "system"]
 4maturity = "production"
 5updated_date = "2024/05/21"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10Detects attempts to execute a program on the host from the Windows Subsystem for Linux. Adversaries may enable and use
11WSL for Linux to avoid detection.
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 = "Execution via Windows Subsystem for Linux"
24references = ["https://learn.microsoft.com/en-us/windows/wsl/wsl-config"]
25risk_score = 47
26rule_id = "db7dbad5-08d2-4d25-b9b1-d3a1e4a15efd"
27severity = "medium"
28tags = [
29    "Domain: Endpoint",
30    "OS: Windows",
31    "Use Case: Threat Detection",
32    "Tactic: Defense Evasion",
33    "Data Source: Elastic Endgame",
34    "Data Source: Elastic Defend",
35]
36timestamp_override = "event.ingested"
37type = "eql"
38
39query = '''
40process where host.os.type == "windows" and event.type : "start" and
41  process.parent.name : ("wsl.exe", "wslhost.exe") and
42  not process.executable : (
43        "?:\\Program Files (x86)\\*",
44        "?:\\Program Files\\*",
45        "?:\\Program Files*\\WindowsApps\\MicrosoftCorporationII.WindowsSubsystemForLinux_*\\wsl*.exe",
46        "?:\\Windows\\System32\\conhost.exe",
47        "?:\\Windows\\System32\\lxss\\wslhost.exe",
48        "?:\\Windows\\System32\\WerFault.exe",
49        "?:\\Windows\\Sys*\\wslconfig.exe"
50  )
51'''
52
53
54[[rule.threat]]
55framework = "MITRE ATT&CK"
56[[rule.threat.technique]]
57id = "T1202"
58name = "Indirect Command Execution"
59reference = "https://attack.mitre.org/techniques/T1202/"
60
61
62[rule.threat.tactic]
63id = "TA0005"
64name = "Defense Evasion"
65reference = "https://attack.mitre.org/tactics/TA0005/"