Detection: Linux EFI Bootloader File Deletion

Updated Date: 2026-07-08 ID: 818a63f8-f2e1-4d1b-ac95-3a4f2ec7f113 Author: Raven Tait, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects file deletions in the EFI boot directory. These files are responsible for initializing the Boot Manager during system startup. Modification or replacement of these files is highly unusual in normal operations and may indicate an attempt to install a bootkit, persist malicious code at the firmware level, or otherwise tamper with the system boot process.

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.action="deleted"
 9Filesystem.file_path="/boot/efi/EFI/BOOT/*"
10Filesystem.file_name="*.efi*"
11
12by Filesystem.file_path Filesystem.file_name Filesystem.user Filesystem.dest
13   Filesystem.action Filesystem.process_guid Filesystem.process_id
14
15
16| `drop_dm_object_name(Filesystem)`
17
18| `security_content_ctime(firstTime)`
19
20| `security_content_ctime(lastTime)`
21
22| `linux_efi_bootloader_file_deletion_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon for Linux EventID 11	Linux	`'sysmon:linux'`	`'Syslog:Linux-Sysmon/Operational'`

Macros Used

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

linux_efi_bootloader_file_deletion_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
T1542.003	Bootkit	Stealth

Exploitation

Installation

DE.CM

CIS 10

APT41

Lazarus Group

CVE

CVE-2024-7344

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 Finding (Notable)	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Intermediate Finding (Risk Event)	No

TTP detections generate a Finding (Notable) and may generate Intermediate Findings (Risk Events) for associated entities.

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 file deletion events including the file path and user context. 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 Filesystem 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 system administrators or package managers may delete or replace EFI bootloader files during system updates or OS reinstallation. Filter for known maintenance windows and authorized administrative activity.

Associated Analytic Story

Finding

Title	Entity Field	Entity Type	Risk Score
Linux EFI bootloader [$file_name$] deletion detected on [$dest$]	dest	system	50

Threat Objects

Field	Type
file_name	file_name

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`
Integration	✅ Passing	Dataset	`Syslog:Linux-Sysmon/Operational`	`sysmon:linux`

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