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Description

The following analytic detects Office products writing .cab or .inf files, indicative of CVE-2021-40444 exploitation. It leverages the Endpoint.Processes and Endpoint.Filesystem data models to identify Office applications creating these file types. This activity is significant as it may signal an attempt to load malicious ActiveX controls and download remote payloads, a known attack vector. If confirmed malicious, this could lead to remote code execution, allowing attackers to gain control over the affected system and potentially compromise sensitive data.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2024-05-27
  • Author: Michael Haag, Splunk
  • ID: f48cd1d4-125a-11ec-a447-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1566 Phishing Initial Access
T1566.001 Spearphishing Attachment Initial Access
Kill Chain Phase
  • Delivery
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_name IN ("winword.exe","excel.exe","powerpnt.exe","mspub.exe","visio.exe","wordpad.exe","wordview.exe","onenote.exe","onenotem.exe","onenoteviewer.exe","onenoteim.exe","msaccess.exe") by _time span=1h Processes.process_id Processes.process_name Processes.process Processes.dest Processes.process_guid 
| `drop_dm_object_name(Processes)` 
|rename process_guid as proc_guid 
| join proc_guid, _time [ 
| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_name IN ("*.inf","*.cab") by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path Filesystem.process_guid 
| `drop_dm_object_name(Filesystem)` 
|rename process_guid as proc_guid 
| fields _time dest file_create_time file_name file_path process_name process_path process proc_guid] 
| dedup file_create_time 
| table dest, process_name, process, file_create_time, file_name, file_path, proc_guid 
| `office_product_writing_cab_or_inf_filter`

Macros

The SPL above uses the following Macros:

:information_source: office_product_writing_cab_or_inf_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • dest
  • process_name
  • process
  • file_create_time
  • file_name
  • file_path

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node and Filesystem node.

Known False Positives

The query is structured in a way that action (read, create) is not defined. Review the results of this query, filter, and tune as necessary. It may be necessary to generate this query specific to your endpoint product.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
80.0 80 100 An instance of $process_name$ was identified on $dest$ writing an inf or cab file to this. This is not typical of $process_name$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 5