ID | Technique | Tactic |
---|---|---|
T1566 | Phishing | Initial Access |
T1566.001 | Spearphishing Attachment | Initial Access |
Detection: Office Product Writing cab or inf
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.
Search
1
2| 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
3| `drop_dm_object_name(Processes)`
4|rename process_guid as proc_guid
5| join proc_guid, _time [
6| 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
7| `drop_dm_object_name(Filesystem)`
8|rename process_guid as proc_guid
9| fields _time dest file_create_time file_name file_path process_name process_path process proc_guid]
10| dedup file_create_time
11| table dest, process_name, process, file_create_time, file_name, file_path, proc_guid
12| `office_product_writing_cab_or_inf_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
CrowdStrike ProcessRollup2 | N/A | 'crowdstrike:events:sensor' |
'crowdstrike' |
N/A |
Macros Used
Name | Value |
---|---|
security_content_summariesonly | summariesonly= summariesonly_config allow_old_summaries= oldsummaries_config fillnull_value= fillnull_config`` |
office_product_writing_cab_or_inf_filter | search * |
office_product_writing_cab_or_inf_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
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 |
Implementation
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
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
An instance of $process_name$ was identified on $dest$ writing an inf or cab file to this. This is not typical of $process_name$. | 80 | 80 | 100 |
References
-
https://twitter.com/vxunderground/status/1436326057179860992?s=20
-
https://app.any.run/tasks/36c14029-9df8-439c-bba0-45f2643b0c70/
-
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444
-
https://twitter.com/RonnyTNL/status/1436334640617373699?s=20
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: 6