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Description

The following analytic identifies the use of a delivered ISO file that has been mounted and the afformention lnk or file opened within it. When the ISO file is opened, the files are saved in the %USER%\AppData\Local\Temp\<random folder name>\ path. The analytic identifies .iso.lnk written to the path. The name of the ISO file is prepended.

  • Type: Hunting
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2022-09-19
  • Author: Michael Haag, Teoderick Contreras, Splunk
  • ID: d7c2c09b-9569-4a9e-a8b6-6a39a99c1d32

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1566.001 Spearphishing Attachment Initial Access
T1566 Phishing Initial Access
T1204.001 Malicious Link Execution
T1204 User Execution Execution
Kill Chain Phase
  • Delivery
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE 


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| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.file_path IN ("*\\Microsoft\\Windows\\Recent\\*") Filesystem.file_name IN ("*.iso.lnk", "*.img.lnk", "*.vhd.lnk", "*vhdx.lnk") by Filesystem.file_create_time Filesystem.process_id Filesystem.file_name Filesystem.file_path Filesystem.dest 
| `drop_dm_object_name(Filesystem)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_iso_lnk_file_creation_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_iso_lnk_file_creation_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.

  • Filesystem.file_create_time
  • Filesystem.process_id
  • Filesystem.file_name
  • Filesystem.file_path
  • Filesystem.dest

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 Filesystem node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Known False Positives

False positives may be high depending on the environment and consistent use of ISOs mounting. Restrict to servers, or filter out based on commonly used ISO names. Filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
40.0 80 50 An ISO file was mounted on $dest$ and should be reviewed and filtered as needed.

: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: 2