Detection: Cisco NVM - Susp Script From Archive Triggering Network Activity

Description

This analytic detects script execution (wscript.exe or cscript.exe) triggered from compressed files opened directly using explorer.exe, winrar.exe, or 7zFM.exe. When a user double clicks on a ".js" file from within one of these compressed files. Its extracted temporally in the temp directory in folder with certain markers. It leverages Cisco Network Visibility Module (NVM) flow data, in order to look for a specific parent/child relationship and an initiated network connection. This behavior is exploited by threat actors such as Scarlet Goldfinch to deliver and run malicious scripts as an initial access technique.

Search

 1`cisco_network_visibility_module_flowdata`
 2parent_process_name IN ("explorer.exe", "winrar.exe", "7zFM.exe")
 3process_name IN ("wscript.exe", "cscript.exe")
 4process_arguments = "*\\AppData\\Local\\Temp\\*"
 5process_arguments IN ("*\\rar*", "*\\7z*", "*.zip*")
 6
 7| stats count min(_time) as firstTime max(_time) as lastTime
 8        values(parent_process_arguments) as parent_process_arguments
 9        values(process_arguments) as process_arguments
10        values(parent_process_hash) as parent_process_hash
11        values(process_hash) as process_hash
12        values(module_name_list) as module_name_list
13        values(module_hash_list) as module_hash_list
14        values(dest_port) as dest_port
15        values(aliul) as additional_logged_in_users_list
16        values(dest_hostname) as dest_hostname
17        by src dest parent_process_path parent_process_name parent_process_integrity_level process_path process_name process_integrity_level process_id transport
18
19| `security_content_ctime(firstTime)`
20
21| `security_content_ctime(lastTime)`
22
23| table 
24  parent_process_integrity_level parent_process_name parent_process_path parent_process_arguments parent_process_hash
25  process_integrity_level process_path process_name process_arguments process_hash process_id
26  additional_logged_in_users_list module_name_list module_hash_list
27  src dest_hostname dest dest_port transport firstTime lastTime
28
29| `cisco_nvm___susp_script_from_archive_triggering_network_activity_filter`

Data Source

Name	Platform	Sourcetype	Source
Cisco Network Visibility Module Flow Data	Network	'cisco:nvm:flowdata'	'not_applicable'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

This search requires Network Visibility Module logs, which includes the flow data sourcetype. This search uses an input macro named cisco_network_visibility_module_flowdata. We strongly recommend that you specify your environment-specific configurations (index, source, sourcetype, etc.) for Cisco Network Visibility Module logs. Replace the macro definition with configurations for your Splunk environment. The search also uses a post-filter macro designed to filter out known false positives. The logs are to be ingested using the Splunk Add-on for Cisco Endpoint Security Analytics (CESA) (https://splunkbase.splunk.com/app/4221).

Known False Positives

Some software installers or automation scripts may extract and run scripts from archive files in temporary directories. However, it is uncommon for such scripts to initiate outbound network connections immediately upon extraction. This behavior should be considered suspicious and investigated, especially in environments where such scripting is not typical.

Associated Analytic Story

• Cisco Network Visibility Module Analytics

Risk Based Analytics (RBA)

Risk Message:

$process_path$ running from $parent_process_name$ with archive-related execution in Temp was observed from host $src$ performing network a connection towards $dest$ / $dest_hostname$ over port $dest_port$.

References

• https://redcanary.com/threat-detection-report/threats/scarlet-goldfinch/

Detection Testing

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