[New] Rare Connection to WebDAV Target (#4667)

rules/windows/credential_access_rare_webdav_destination.toml

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+[metadata]
+creation_date = "2025/04/28"
+integration = ["endpoint", "system", "windows", "m365_defender", "crowdstrike"]
+maturity = "production"
+updated_date = "2025/04/28"
+min_stack_version = "8.17.0"
+min_stack_comments = "Elastic ES|QL VALUES aggregation is more performant in 8.16.5 and above."
+
+[rule]
+author = ["Elastic"]
+description = """
+Identifies rare connection attempts to a Web Distributed Authoring and Versioning (WebDAV) resource. Attackers may inject
+WebDAV paths in files or features opened by a victim user to leak their NTLM credentials via forced authentication.
+"""
+from = "now-3660s"
+language = "esql"
+license = "Elastic License v2"
+name = "Rare Connection to WebDAV Target"
+note = """## Triage and analysis
+
+### Investigating Rare Connection to WebDAV Target
+
+### Possible investigation steps
+
+- Examine the reputation of the destination domain or IP address.
+- Verify if the target user opened any attachments or clicked links pointing to the same target within seconds from the alert timestamp.
+- Correlate the findings with other security logs and alerts to identify any patterns or additional indicators of compromise related to the potential relay attack.
+
+### False positive analysis
+
+- User accessing legit WebDAV resources.
+
+### Response and remediation
+
+- Conduct a password reset for the target account that may have been compromised or are at risk, ensuring the use of strong, unique passwords.
+- Verify whether other users were targeted but did not open the lure..
+- 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.
+- 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."""
+references = ["https://attack.mitre.org/techniques/T1187/"]
+risk_score = 47
+rule_id = "6756ee27-9152-479b-9b73-54b5bbda301c"
+severity = "medium"
+tags = [
+    "Domain: Endpoint",
+    "OS: Windows",
+    "Use Case: Threat Detection",
+    "Tactic: Credential Access",
+    "Data Source: Elastic Defend",
+    "Data Source: Windows Security Event Logs",
+    "Data Source: Microsoft Defender for Endpoint",
+    "Data Source: Crowdstrike",
+    "Resources: Investigation Guide",
+]
+timestamp_override = "event.ingested"
+type = "esql"
+
+query = '''
+FROM logs-*
+| where @timestamp > NOW() - 8 hours
+| WHERE event.category == "process" and event.type == "start" and process.name == "rundll32.exe" and process.command_line like "*DavSetCookie*"
+| keep host.id, process.command_line, user.name
+| grok process.command_line """(?<target>DavSetCookie .* http)"""
+| eval webdav_target = REPLACE(target, "(DavSetCookie | http)", "")
+| 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})"""
+| stats total = count(*), unique_count_host = count_distinct(host.id), hosts = VALUES(host.id), users = VALUES(user.name) by webdav_target
+| where unique_count_host == 1 and total <= 3
+'''
+
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+[[rule.threat.technique]]
+id = "T1187"
+name = "Forced Authentication"
+reference = "https://attack.mitre.org/techniques/T1187/"
+
+
+[rule.threat.tactic]
+id = "TA0006"
+name = "Credential Access"
+reference = "https://attack.mitre.org/tactics/TA0006/"
+