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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-endpoint.events.process-*, logs-windows.sysmon_operational-*, logs-system.security-*, logs-windows.*, winlogbeat-*, logs-crowdstrike.fdr*, logs-m365_defender.event-* METADATA _id, _version, _index
| where
    @timestamp > now() - 8 hours and
    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, user.id
| grok process.command_line """(?<Esql.server_webdav_server>([a-zA-Z0-9-]{4,}\.[a-zA-Z]{2,3}@SSL)|((\d{1,3}\.){3}\d{1,3}))"""
| where
    Esql.server_webdav_server is not null and
    not Esql.server_webdav_server in ("www.google.com@SSL", "www.elastic.co@SSL", "sharepoint.com@SSL", "live.net@SSL", "google.com@SSL", "SHAREPOINT.COM@SSL", "github.com@SSL") and
    not Esql.server_webdav_server 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
    Esql.event_count = count(*),
    Esql.host_id_count_distinct = count_distinct(host.id),
    Esql.user_id_count_distinct = count_distinct(user.id),
    Esql.host_id_values = values(host.id),
    Esql.user_name_values = values(user.name)
  by Esql.server_webdav_server
| where
    Esql.host_id_count_distinct == 1 and
    Esql.event_count <= 3 and Esql.user_id_count_distinct == 1
| eval host.id = MV_MIN(Esql.host_id_values), user.name = MV_MIN(Esql.user_name_values), destination.domain = MV_MIN(Esql.server_webdav_server)
| KEEP host.id, user.name, destination.domain, Esql.*

Framework: MITRE ATT&CK