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Description

The following analytic detects file writes with extensions indicative of a SamSam ransomware attack. It leverages file-system activity data to identify file names ending in .stubbin, .berkshire, .satoshi, .sophos, or .keyxml. This activity is significant because SamSam ransomware is highly destructive, leading to file encryption and ransom demands. If confirmed malicious, the impact includes significant financial losses, operational disruptions, and reputational damage. Immediate actions should include isolating affected systems, restoring files from backups, and investigating the attack source to prevent further incidents.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2024-05-22
  • Author: Rico Valdez, Splunk
  • ID: 02c6cfc2-ae66-4735-bfc7-6291da834cbf

Annotations

ATT&CK
Kill Chain Phase
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime values(Filesystem.user) as user values(Filesystem.dest) as dest values(Filesystem.file_path) as file_path from datamodel=Endpoint.Filesystem by Filesystem.file_name 
| `drop_dm_object_name(Filesystem)` 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)`
| rex field=file_name "(?<file_extension>\.[^\.]+)$" 
| search file_extension=.stubbin OR file_extension=.berkshire OR file_extension=.satoshi OR file_extension=.sophos OR file_extension=.keyxml 
| `file_with_samsam_extension_filter`

Macros

The SPL above uses the following Macros:

:information_source: file_with_samsam_extension_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
  • Filesystem.user
  • Filesystem.dest
  • Filesystem.file_path
  • Filesystem.file_name

How To Implement

You must be ingesting data that records file-system activity from your hosts to populate the Endpoint file-system data-model node. If you are using Sysmon, you will need a Splunk Universal Forwarder on each endpoint from which you want to collect data.

Known False Positives

Because these extensions are not typically used in normal operations, you should investigate all results.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
90.0 100 90 File writes $file_name$ with extensions consistent with a SamSam ransomware attack seen on $dest$

: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