Linux Possible Ssh Key File Creation

SPLUNK detection rule by Teoderick Contreras, Splunk · Apache-2.0

The following analytic detects the creation of SSH key files in the ~/.ssh/ directory. It leverages filesystem data to identify new files in this specific path. This activity is significant because threat actors often create SSH keys to gain persistent access and escalate privileges on a compromised host. If confirmed malicious, this could allow attackers to remotely access the machine using the OpenSSH daemon service, leading to potential unauthorized control and data exfiltration.

name: Linux Possible Ssh Key File Creation
id: c04ef40c-72da-11ec-8eac-acde48001122
version: 12
creation_date: '2022-01-12'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: The following analytic detects the creation of SSH key files in the ~/.ssh/ directory. It leverages filesystem data to identify new files in this specific path. This activity is significant because threat actors often create SSH keys to gain persistent access and escalate privileges on a compromised host. If confirmed malicious, this could allow attackers to remotely access the machine using the OpenSSH daemon service, leading to potential unauthorized control and data exfiltration.
data_source:
    - Sysmon for Linux EventID 11
search: |-
    | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem
      WHERE Filesystem.file_path IN ("*/.ssh*")
      BY Filesystem.action Filesystem.dest Filesystem.file_access_time
         Filesystem.file_create_time Filesystem.file_hash Filesystem.file_modify_time
         Filesystem.file_name Filesystem.file_path Filesystem.file_acl
         Filesystem.file_size Filesystem.process_guid Filesystem.process_id
         Filesystem.user Filesystem.vendor_product
    | `drop_dm_object_name(Filesystem)`
    | `security_content_ctime(lastTime)`
    | `security_content_ctime(firstTime)`
    | `linux_possible_ssh_key_file_creation_filter`
how_to_implement: To successfully implement this search, you need to be ingesting logs with the file name, file path, and process_guid executions from your endpoints. If you are using Sysmon, you can use the Add-on for Linux Sysmon from Splunkbase.
known_false_positives: Administrator or network operator can create file in ~/.ssh folders for automation purposes. Please update the filter macros to remove false positives.
references:
    - https://www.hackingarticles.in/ssh-penetration-testing-port-22/
    - https://attack.mitre.org/techniques/T1098/004/
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | 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: 7d
      latest_offset: "0"
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: A file $file_name$ is created in $file_path$ on $dest$
analytic_story:
    - Linux Privilege Escalation
    - Linux Persistence Techniques
    - Linux Living Off The Land
    - Hellcat Ransomware
asset_type: Endpoint
mitre_attack_id:
    - T1098.004
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
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/sysmon_linux.log
          source: Syslog:Linux-Sysmon/Operational
          sourcetype: sysmon:linux
      test_type: unit

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5cddc2b7-aec5-425c-bc87-0170f12762d6

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Executable code, not a declarative rule

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