Rare Connection to WebDAV Target

 1[metadata]
 2creation_date = "2025/04/28"
 3integration = ["endpoint", "system", "windows", "m365_defender", "crowdstrike"]
 4maturity = "production"
 5updated_date = "2025/04/28"
 6min_stack_version = "8.17.0"
 7min_stack_comments = "Elastic ES|QL VALUES aggregation is more performant in 8.16.5 and above."
 8
 9[rule]
10author = ["Elastic"]
11description = """
12Identifies rare connection attempts to a Web Distributed Authoring and Versioning (WebDAV) resource. Attackers may inject
13WebDAV paths in files or features opened by a victim user to leak their NTLM credentials via forced authentication.
14"""
15from = "now-3660s"
16language = "esql"
17license = "Elastic License v2"
18name = "Rare Connection to WebDAV Target"
19note = """## Triage and analysis
20
21### Investigating Rare Connection to WebDAV Target
22
23### Possible investigation steps
24
25- Examine the reputation of the destination domain or IP address.
26- Verify if the target user opened any attachments or clicked links pointing to the same target within seconds from the alert timestamp.
27- Correlate the findings with other security logs and alerts to identify any patterns or additional indicators of compromise related to the potential relay attack.
28
29### False positive analysis
30
31- User accessing legit WebDAV resources.
32
33### Response and remediation
34
35- Conduct a password reset for the target account that may have been compromised or are at risk, ensuring the use of strong, unique passwords.
36- Verify whether other users were targeted but did not open the lure..
37- Escalate the incident to the security operations center (SOC) or incident response team for further investigation and to determine the full scope of the breach.
38- Conduct a post-incident review to identify any gaps in security controls and update policies or procedures to prevent recurrence, ensuring lessons learned are applied to improve overall security posture."""
39references = ["https://attack.mitre.org/techniques/T1187/"]
40risk_score = 47
41rule_id = "6756ee27-9152-479b-9b73-54b5bbda301c"
42severity = "medium"
43tags = [
44    "Domain: Endpoint",
45    "OS: Windows",
46    "Use Case: Threat Detection",
47    "Tactic: Credential Access",
48    "Data Source: Elastic Defend",
49    "Data Source: Windows Security Event Logs",
50    "Data Source: Microsoft Defender for Endpoint",
51    "Data Source: Crowdstrike",
52    "Resources: Investigation Guide",
53]
54timestamp_override = "event.ingested"
55type = "esql"
56
57query = '''
58FROM logs-*
59| where @timestamp > NOW() - 8 hours
60| WHERE event.category == "process" and event.type == "start" and process.name == "rundll32.exe" and process.command_line like "*DavSetCookie*"
61| keep host.id, process.command_line, user.name
62| grok process.command_line """(?<target>DavSetCookie .* http)"""
63| eval webdav_target = REPLACE(target, "(DavSetCookie | http)", "")
64| where webdav_target is not null and webdav_target rlike """(([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,3}(@SSL.*)*|(\d{1,3}\.){3}\d{1,3})""" and not webdav_target in ("www.google.com@SSL", "www.elastic.co@SSL") and not webdav_target rlike """(10\.(\d{1,3}\.){2}\d{1,3}|172\.(1[6-9]|2\d|3[0-1])\.(\d{1,3}\.)\d{1,3}|192\.168\.(\d{1,3}\.)\d{1,3})"""
65| stats total = count(*), unique_count_host = count_distinct(host.id), hosts = VALUES(host.id), users = VALUES(user.name) by webdav_target
66| where unique_count_host == 1 and total <= 3
67'''
68
69
70[[rule.threat]]
71framework = "MITRE ATT&CK"
72[[rule.threat.technique]]
73id = "T1187"
74name = "Forced Authentication"
75reference = "https://attack.mitre.org/techniques/T1187/"
76
77
78[rule.threat.tactic]
79id = "TA0006"
80name = "Credential Access"
81reference = "https://attack.mitre.org/tactics/TA0006/"