Rare Connection to WebDAV Target

 1[metadata]
 2creation_date = "2025/04/28"
 3integration = ["endpoint", "system", "windows", "m365_defender", "crowdstrike"]
 4maturity = "production"
 5updated_date = "2025/07/16"
 6
 7[rule]
 8author = ["Elastic"]
 9description = """
10Identifies rare connection attempts to a Web Distributed Authoring and Versioning (WebDAV) resource. Attackers may
11inject WebDAV paths in files or features opened by a victim user to leak their NTLM credentials via forced
12authentication.
13"""
14from = "now-3660s"
15language = "esql"
16license = "Elastic License v2"
17name = "Rare Connection to WebDAV Target"
18note = """## Triage and analysis
19
20### Investigating Rare Connection to WebDAV Target
21
22### Possible investigation steps
23
24- Examine the reputation of the destination domain or IP address.
25- Verify if the target user opened any attachments or clicked links pointing to the same target within seconds from the alert timestamp.
26- Correlate the findings with other security logs and alerts to identify any patterns or additional indicators of compromise related to the potential relay attack.
27
28### False positive analysis
29
30- User accessing legit WebDAV resources.
31
32### Response and remediation
33
34- Conduct a password reset for the target account that may have been compromised or are at risk, ensuring the use of strong, unique passwords.
35- Verify whether other users were targeted but did not open the lure..
36- 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.
37- 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."""
38references = ["https://attack.mitre.org/techniques/T1187/"]
39risk_score = 47
40rule_id = "6756ee27-9152-479b-9b73-54b5bbda301c"
41severity = "medium"
42tags = [
43    "Domain: Endpoint",
44    "OS: Windows",
45    "Use Case: Threat Detection",
46    "Tactic: Credential Access",
47    "Data Source: Elastic Defend",
48    "Data Source: Windows Security Event Logs",
49    "Data Source: Microsoft Defender for Endpoint",
50    "Data Source: Crowdstrike",
51    "Resources: Investigation Guide",
52]
53timestamp_override = "event.ingested"
54type = "esql"
55
56query = '''
57from logs-*
58| where
59    @timestamp > now() - 8 hours and
60    event.category == "process" and
61    event.type == "start" and
62    process.name == "rundll32.exe" and
63    process.command_line like "*DavSetCookie*"
64| keep host.id, process.command_line, user.name
65| grok
66    process.command_line """(?<Esql.server_webdav_cookie>DavSetCookie .* http)"""
67| eval
68    Esql.server_webdav_cookie_replace = replace(Esql.server_webdav_cookie, "(DavSetCookie | http)", "")
69| where
70    Esql.server_webdav_cookie_replace is not null and
71    Esql.server_webdav_cookie_replace rlike """(([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,3}(@SSL.*)*|(\d{1,3}\.){3}\d{1,3})""" and
72    not Esql.server_webdav_cookie_replace in ("www.google.com@SSL", "www.elastic.co@SSL") and
73    not Esql.server_webdav_cookie_replace 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})"""
74| stats
75    Esql.event_count = count(*),
76    Esql.host_id_count_distinct = count_distinct(host.id),
77    Esql.host_id_values = values(host.id),
78    Esql.user_name_values = values(user.name)
79  by Esql.server_webdav_cookie_replace
80| where
81    Esql.host_id_count_distinct == 1 and
82    Esql.event_count <= 3
83'''
84
85
86[[rule.threat]]
87framework = "MITRE ATT&CK"
88[[rule.threat.technique]]
89id = "T1187"
90name = "Forced Authentication"
91reference = "https://attack.mitre.org/techniques/T1187/"
92
93
94[rule.threat.tactic]
95id = "TA0006"
96name = "Credential Access"
97reference = "https://attack.mitre.org/tactics/TA0006/"