Rare Connection to WebDAV Target
ELASTIC detection rule by Elastic · Elastic License v2
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.
[metadata]
creation_date = "2025/04/28"
integration = ["endpoint", "system", "windows", "m365_defender", "crowdstrike"]
maturity = "production"
updated_date = "2026/08/18"
[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-8h"
interval="1h"
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 XDR",
"Data Source: Crowdstrike",
"Resources: Investigation Guide",
]
timestamp_override = "event.ingested"
type = "esql"
query = '''
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
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
// extract the host from the WebDAV URL authority, excluding optional credentials and port
| grok process.command_line """(?i:https?)://(?:[^/@\s]+@)?(?<Esql.server_webdav_server>[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*)"""
| eval Esql.server_webdav_server = TO_LOWER(Esql.server_webdav_server)
| where
Esql.server_webdav_server is not null and
not Esql.server_webdav_server in ("www.google.com", "www.elastic.co", "google.com", "github.com", "www.github.com", "sharepoint.com", "live.net") and
not Esql.server_webdav_server like ("*.live.net", "*.sharepoint.com") and
// excludes private IP ranges
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.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
| 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.*
'''
setup = """## Setup
This rule is designed for data generated by [Elastic Defend](https://www.elastic.co/security/endpoint-security), which provides native endpoint detection and response, along with event enrichments designed to work with our detection rules.
Setup instructions: https://ela.st/install-elastic-defend
### Additional data sources
This rule also supports the following third-party data sources. For setup instructions, refer to the links below:
- [CrowdStrike](https://ela.st/crowdstrike-integration)
- [Microsoft Defender XDR](https://ela.st/m365-defender)
- [Sysmon Event ID 1 - Process Creation](https://ela.st/sysmon-event-1-setup)
- [Windows Process Creation Logs](https://ela.st/audit-process-creation)
"""
[[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/"
[[rule.threat]]
framework = "MITRE ATT&CK"
[[rule.threat.technique]]
id = "T1218"
name = "System Binary Proxy Execution"
reference = "https://attack.mitre.org/techniques/T1218/"
[[rule.threat.technique.subtechnique]]
id = "T1218.011"
name = "Rundll32"
reference = "https://attack.mitre.org/techniques/T1218/011/"
[rule.threat.tactic]
id = "TA0005"
name = "Defense Evasion"
reference = "https://attack.mitre.org/tactics/TA0005/"