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Rare Connection to WebDAV Target

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.

Rule type: esql
Rule indices:

Rule Severity: medium
Risk Score: 47
Runs every:
Searches indices from: now-3660s
Maximum alerts per execution: ?
References:

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

Version: ?
Rule authors:

  • Elastic

Rule license: Elastic License v2

  • 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.
  • User accessing legit WebDAV resources.
  • 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.
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

Framework: MITRE ATT&CK