splunk-security_content/detections/endpoint/linux_indicator_removal_clear_cache.yml

name: Linux Indicator Removal Clear Cache
id: e0940505-0b73-4719-84e6-cb94c44a5245
version: 1
date: '2023-04-14'
author: Teoderick Contreras, Splunk
status: production
type: TTP
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.
data_source:
- Sysmon Event ID 1
search: '| 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`'
how_to_implement: The detection is based on data that originates from Endpoint Detection
  and Response (EDR) agents. These agents are designed to provide security-related
  telemetry from the endpoints where the agent is installed. To implement this search,
  you must ingest logs that contain the process GUID, process name, and parent process.
  Additionally, you must ingest complete command-line executions. These logs must
  be processed using the appropriate Splunk Technology Add-ons that are specific to
  the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint`
  data model. Use the Splunk Common Information Model (CIM) to normalize the field
  names and speed up the data modeling process.
known_false_positives: unknown
references:
- https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/overview-of-the-cyber-weapons-used-in-the-ukraine-russia-war/
- https://cert.gov.ua/article/3718487
tags:
  analytic_story:
  - AwfulShred
  - Data Destruction
  asset_type: Endpoint
  confidence: 70
  impact: 70
  message: a $process_name$ clear cache using kernel drop cache system request in
    $dest$
  mitre_attack_id:
  - T1070
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  - name: user
    type: User
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Processes.dest
  - Processes.user
  - Processes.parent_process_name
  - Processes.process_name
  - Processes.process
  - Processes.process_id
  - Processes.parent_process_id
  risk_score: 49
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/malware/awfulshred/test3/sysmon_linux.log
    source: Syslog:Linux-Sysmon/Operational
    sourcetype: sysmon_linux
    update_timestamp: true