GitHub Repo

Detection: Windows Cabinet File Extraction Via Expand

Updated Date: 2025-09-18 ID: 4e3e3b8c-6d3a-4b47-9f5a-9e3e0a0a6f2f Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

Detects usage of expand.exe to extract Microsoft Cabinet (CAB) archives, with emphasis on extractions into C:\\ProgramData or similar staging locations. In recent APT37 activity, a CAB payload (e.g., wonder.cab) was expanded into ProgramData prior to persistence and execution. This behavior is a strong signal for ingress tool transfer and staging of payloads.

 1
 2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime
 3from datamodel=Endpoint.Processes
 4where Processes.process_name="expand.exe"
 5  (Processes.process="*-F:*" OR Processes.process="*/F:*")
 6  Processes.process="*\\ProgramData\\*"
 7by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.original_file_name Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_path Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_path Processes.user_id Processes.vendor_product
 8
 9| `drop_dm_object_name(Processes)`
10
11| `security_content_ctime(firstTime)`
12
13| `security_content_ctime(lastTime)`
14
15| `windows_cabinet_file_extraction_via_expand_filter`

Data Source

Name Platform Sourcetype Source
CrowdStrike ProcessRollup2 N/A 'crowdstrike:events:sensor' 'crowdstrike'
Sysmon EventID 1 Windows icon Windows 'XmlWinEventLog' 'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688 Windows icon Windows 'XmlWinEventLog' 'XmlWinEventLog:Security'

Macros Used

Name Value
security_content_ctime convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)
windows_cabinet_file_extraction_via_expand_filter search *
windows_cabinet_file_extraction_via_expand_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
T1105 Ingress Tool Transfer Command And Control
Command and Control
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

This analytic relies on process creation telemetry mapped to the Endpoint.Processes datamodel (e.g., Sysmon EID 1 or EDR). Ensure full command-line logging is enabled to capture expand.exe arguments, including /F:* or -F:* and destination paths.

Known False Positives

Legitimate software deployment or administrators may use expand.exe for local file extraction. Filter by approved deployment tools, signed parent processes, and sanctioned paths.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

expand.exe extracted cabinet contents on $dest$ executed by $user$.

Risk Object Risk Object Type Risk Score Threat Objects
user system 30 process_name
dest system 30 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: 1