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Description

This analytic is to look for possible ssh key file creation on ~/.ssh/ folder. This technique is commonly abused by threat actors and adversaries to gain persistence and privilege escalation to the targeted host. by creating ssh private and public key and passing the public key to the attacker server. threat actor can access remotely the machine using openssh daemon service.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2022-01-11
  • Author: Teoderick Contreras, Splunk
  • ID: c04ef40c-72da-11ec-8eac-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1098.004 SSH Authorized Keys Persistence
T1098 Account Manipulation Persistence
Kill Chain Phase
  • Installation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


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| 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.dest Filesystem.file_name Filesystem.process_guid Filesystem.file_path 
| `drop_dm_object_name(Filesystem)` 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)` 
| `linux_possible_ssh_key_file_creation_filter`

Macros

The SPL above uses the following Macros:

:information_source: linux_possible_ssh_key_file_creation_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
  • Filesystem.dest
  • Filesystem.file_create_time
  • Filesystem.file_name
  • Filesystem.process_guid
  • Filesystem.file_path

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.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
36.0 60 60 A file $file_name$ is created in $file_path$ on $dest$

: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

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