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Description

This analytic looks for processes that clear or free page cache in Linux system host. This technique was seen in Awfulshred malware wiper that tries to clear the cache using kernel system request drop_caches while wiping all files in the targeted host. This TTP detection can be a good indicator of user or process tries to clear page cache to delete tracks or might be a wiper like Awfulshred.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2023-02-09
  • Author: Teoderick Contreras, Splunk
  • ID: e0940505-0b73-4719-84e6-cb94c44a5245

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1070 Indicator Removal Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE 


1
2
3
4
5



| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name IN ("dash", "sudo", "bash")  AND Processes.process  IN("* echo 3 > *", "* echo 2 > *","* echo 1 > *") AND Processes.process = "*/proc/sys/vm/drop_caches" by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.process_guid 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `linux_indicator_removal_clear_cache_filter`

Macros

The SPL above uses the following Macros:

:information_source: linux_indicator_removal_clear_cache_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
  • Processes.dest
  • Processes.user
  • Processes.parent_process_name
  • Processes.process_name
  • Processes.process
  • Processes.process_id
  • Processes.parent_process_id

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from Splunkbase.

Known False Positives

unknown

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
49.0 70 70 a $process_name$ clear cache using kernel drop cache system request in $dest$

: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: 1