splunk-security_content/detections/endpoint/linux_indicator_removal_clear_cache.yml

name: Linux Indicator Removal Clear Cache
id: e0940505-0b73-4719-84e6-cb94c44a5245
version: 4
date: '2024-11-13'
author: Teoderick Contreras, Splunk
status: production
type: TTP
description: The following analytic detects processes that clear or free page cache
  on a Linux system. It leverages Endpoint Detection and Response (EDR) data, focusing
  on specific command-line executions involving the kernel system request `drop_caches`.
  This activity is significant as it may indicate an attempt to delete forensic evidence
  or the presence of wiper malware like Awfulshred. If confirmed malicious, this behavior
  could allow an attacker to cover their tracks, making it difficult to investigate
  other malicious activities or system compromises.
data_source:
- Sysmon for Linux EventID 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
drilldown_searches:
- name: View the detection results for - "$dest$" and "$user$"
  search: '%original_detection_search% | search  dest = "$dest$" user = "$user$"'
  earliest_offset: $info_min_time$
  latest_offset: $info_max_time$
- name: View risk events for the last 7 days for - "$dest$" and "$user$"
  search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$",
    "$user$") starthoursago=168  | stats count min(_time) as firstTime max(_time)
    as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk
    Message" values(analyticstories) as "Analytic Stories" values(annotations._all)
    as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics"
    by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
  earliest_offset: $info_min_time$
  latest_offset: $info_max_time$
rba:
  message: a $process_name$ clear cache using kernel drop cache system request in
    $dest$
  risk_objects:
  - field: dest
    type: system
    score: 49
  - field: user
    type: user
    score: 49
  threat_objects: []
tags:
  analytic_story:
  - AwfulShred
  - Data Destruction
  asset_type: Endpoint
  mitre_attack_id:
  - T1070
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  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