Detection: Windows Universal Data Link File Creation

Updated Date: 2026-04-13 ID: aac9ade1-dc8b-4f15-9586-4665d01b8645 Author: Raven Tait, Splunk Type: Anomaly Product: Splunk Enterprise Security

Description

Detects the creation of Universal Data Link (UDL) files. This could indicate a phishing technique that exploits UDL files, which are typically used in Windows for database connections. Attackers might leverage UDL files to bypass email filters and capture user credentials by tricking victims into testing a connection to a malicious server.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6from datamodel=Endpoint.Filesystem where
 7
 8Filesystem.file_name="*.udl"
 9Filesystem.action="created"
10
11by Filesystem.dest Filesystem.file_create_time Filesystem.process_path
12   Filesystem.process_guid Filesystem.process_id Filesystem.file_path
13   Filesystem.action Filesystem.file_name Filesystem.user
14   Filesystem.vendor_product
15
16
17| `drop_dm_object_name(Filesystem)`
18
19| `security_content_ctime(firstTime)`
20
21| `security_content_ctime(lastTime)`
22
23| `windows_universal_data_link_file_creation_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 11	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_universal_data_link_file_creation_filter	`search *`

windows_universal_data_link_file_creation_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
T1204.002	Malicious File	Execution
T1566.001	Spearphishing Attachment	Initial Access

Delivery

Installation

DE.AE

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 Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

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

Legitimate database administrators or developers may create UDL files for routine connection testing. Filter alerts based on trusted user activity to reduce false positives.

Associated Analytic Story

Spearphishing Attachments

Risk Based Analytics (RBA)

Risk Message:

UDL file created at $file_path$ on $dest$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	20	file_path

References

https://trustedsec.com/blog/oops-i-udld-it-again

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: 1