Detection: Windows Rundll32 WebDav With Network Connection

Updated Date: 2025-06-10 ID: f03355e0-28b5-4e9b-815a-6adffc63b38c Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the execution of rundll32.exe with command-line arguments loading davclnt.dll and the davsetcookie function to access a remote WebDav instance. It uses data from Endpoint Detection and Response (EDR) agents, correlating process execution and network traffic data. This activity is significant as it may indicate exploitation of CVE-2023-23397, a known vulnerability. If confirmed malicious, this could allow an attacker to establish unauthorized remote connections, potentially leading to data exfiltration or further network compromise.

 1
 2| tstats `security_content_summariesonly` count 
 3  min(_time) as firstTime 
 4  max(_time) as lastTime 
 5FROM datamodel=Endpoint.Processes where 
 6  Processes.parent_process_name=svchost.exe
 7  `process_rundll32` 
 8  Processes.process IN (
 9    "*\\windows\\system32\\davclnt.dll,*davsetcookie*", 
10    "*\\windows\\syswow64\\davclnt.dll,*davsetcookie*") 
11by host _time span=1h 
12  Processes.action Processes.dest Processes.original_file_name Processes.parent_process 
13  Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id 
14  Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec 
15  Processes.process_guid Processes.process_hash  Processes.process_id Processes.process_integrity_level 
16  Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product 
17
18| `drop_dm_object_name(Processes)` 
19
20| `security_content_ctime(firstTime)`
21
22| `security_content_ctime(lastTime)` 
23
24| rename dest as src 
25
26| join host process_id
27[
28  
29| tstats `security_content_summariesonly` count 
30    latest(All_Traffic.dest) as dest
31    latest(All_Traffic.dest_ip) as dest_ip 
32    latest(All_Traffic.dest_port) as dest_port
33  FROM datamodel=Network_Traffic.All_Traffic where 
34    All_Traffic.dest_port!=0 
35    NOT (All_Traffic.dest_ip IN (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16)) 
36  by host All_Traffic.action All_Traffic.app All_Traffic.bytes All_Traffic.bytes_in All_Traffic.bytes_out
37          All_Traffic.dest  All_Traffic.dest_ip All_Traffic.dest_port All_Traffic.dvc All_Traffic.protocol
38          All_Traffic.protocol_version All_Traffic.src All_Traffic.src_ip All_Traffic.src_port
39          All_Traffic.transport All_Traffic.user All_Traffic.vendor_product All_Traffic.direction
40          All_Traffic.process_id
41  
42| `drop_dm_object_name(All_Traffic)`
43] 
44
45| `windows_rundll32_webdav_with_network_connection_filter`

Data Source

Name Platform Sourcetype Source
Sysmon EventID 1 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Sysmon EventID 3 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Name Value
process_rundll32 (Processes.process_name=rundll32.exe OR Processes.original_file_name=RUNDLL32.EXE)
windows_rundll32_webdav_with_network_connection_filter search *
windows_rundll32_webdav_with_network_connection_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1048.003 Exfiltration Over Unencrypted Non-C2 Protocol Exfiltration
Actions on Objectives
DE.CM
CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

False positives will be present based on legitimate software, filtering may need to occur.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to contact a remote WebDav server.

Risk Object Risk Object Type Risk Score Threat Objects
dest system 48 parent_process_name, process_name
user user 48 parent_process_name, process_name

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-Sysmon/Operational XmlWinEventLog

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 8