Detection: Windows Suspicious File in EFI Volume

Updated Date: 2026-04-13 ID: 4000d728-faaf-44d4-969b-12216f2879e1 Author: Raven Tait, Splunk Type: TTP Product: Splunk Enterprise Security

Description

Detects data files in the EFI volume. This is sometimes indicative of an actor attempting to bypass secure boot through vulnerabilities such as CVE-2024-7344. These use vulnerable boot loaders to run malicious system firmware code.

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_path="*\\EFI\\Boot\\*"
 9Filesystem.file_path="*.dat"
10
11by Filesystem.dest Filesystem.file_create_time Filesystem.process_path
12   Filesystem.process_guid Filesystem.process_id Filesystem.file_path Filesystem.file_name
13   Filesystem.action Filesystem.user Filesystem.vendor_product
14
15
16| `drop_dm_object_name(Filesystem)`
17
18| `security_content_ctime(firstTime)`
19
20| `security_content_ctime(lastTime)`
21
22| `windows_suspicious_file_in_efi_volume_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_suspicious_file_in_efi_volume_filter	`search *`

windows_suspicious_file_in_efi_volume_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
T1542.001	System Firmware	Persistence
T1490	Inhibit System Recovery	Stealth

Actions on Objectives

Exploitation

Installation

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

Some legitimate system or firmware update processes may create or modify files in the EFI volume. Review alerts carefully to distinguish between normal maintenance and suspicious activity.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

Suspicious EFI volume data file created at $file_path$ on $dest$.

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	50	file_path

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: 1