name: Linux SSH Authorized Keys Modification
id: f5ab595e-28e5-4327-8077-5008ba97c850
version: 1
date: '2022-07-27'
author: Michael Haag, Splunk
status: production
type: Anomaly
description: The following analytic identifies based on process execution the modification
  of SSH Authorized Keys. Adversaries perform this behavior to persist on endpoints.
  During triage, review parallel processes and capture any additional file modifications
  for review.
data_source:
- Sysmon Event ID 1
search:
  selection1:
    CommandLine: '*/authorized_keys*'
    Image|endswith:
    - bash
    - cat
  condition: selection1
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 `Processes` 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: Filtering will be required as system administrators will add
  and remove. One way to filter query is to add "echo".
references:
- https://redcanary.com/blog/lateral-movement-with-secure-shell/
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1098.004/T1098.004.md
tags:
  analytic_story:
  - Linux Living Off The Land
  asset_type: Endpoint
  confidence: 50
  impact: 30
  message: An instance of $parent_process_name$ spawning $process_name$ was identified
    on endpoint $dest$ by user $user$ modifying SSH Authorized Keys.
  mitre_attack_id:
  - T1098.004
  observable:
  - name: user
    type: User
    role:
    - Victim
  - name: dest
    type: Hostname
    role:
    - Victim
  - name: parent_process_name
    type: Process
    role:
    - Parent Process
  - name: process_name
    type: Process
    role:
    - Child Process
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  risk_score: 15
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1098.004/ssh_authorized_keys/authkey_linux-sysmon.log
    source: Syslog:Linux-Sysmon/Operational
    sourcetype: sysmon:linux
    update_timestamp: true