Host Files System Changes via Windows Subsystem for Linux

 1[metadata]
 2creation_date = "2023/01/12"
 3integration = ["endpoint", "windows"]
 4maturity = "production"
 5updated_date = "2023/06/22"
 6min_stack_comments = "New fields added: required_fields, related_integrations, setup"
 7min_stack_version = "8.3.0"
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Detects files creation and modification on the host system from the the Windows Subsystem for Linux. 
13Adversaries may enable and use WSL for Linux to avoid detection.
14"""
15from = "now-9m"
16index = ["winlogbeat-*", "logs-endpoint.events.*", "logs-windows.*", "endgame-*"]
17language = "eql"
18license = "Elastic License v2"
19name = "Host Files System Changes via Windows Subsystem for Linux"
20references = ["https://github.com/microsoft/WSL"]
21risk_score = 47
22rule_id = "e88d1fe9-b2f4-48d4-bace-a026dc745d4b"
23severity = "medium"
24tags = ["Domain: Endpoint", "OS: Windows", "Use Case: Threat Detection", "Tactic: Defense Evasion", "Data Source: Elastic Endgame", "Data Source: Elastic Defend"]
25timestamp_override = "event.ingested"
26type = "eql"
27
28query = '''
29sequence by process.entity_id with maxspan=5m
30 [process where host.os.type == "windows" and event.type == "start" and
31  process.name : "dllhost.exe" and 
32   /* Plan9FileSystem CLSID - WSL Host File System Worker */
33  process.command_line : "*{DFB65C4C-B34F-435D-AFE9-A86218684AA8}*"]
34 [file where host.os.type == "windows" and process.name : "dllhost.exe" and not file.path : "?:\\Users\\*\\Downloads\\*"]
35'''
36
37
38[[rule.threat]]
39framework = "MITRE ATT&CK"
40[[rule.threat.technique]]
41id = "T1202"
42name = "Indirect Command Execution"
43reference = "https://attack.mitre.org/techniques/T1202/"
44
45
46[rule.threat.tactic]
47id = "TA0005"
48name = "Defense Evasion"
49reference = "https://attack.mitre.org/tactics/TA0005/"