This analytic is to detect a deletion of ssh key in a linux machine. attacker may delete or modify ssh key to impair some security features or act as defense evasion in compromised linux machine. This Anomaly can be also a good indicator of a malware trying to wipe or delete several files in a compromised host as part of its destructive payload like what acidrain malware does in linux or router machines. This detection can be a good pivot to check what process and user tries to delete this type of files which is not so common and need further investigation.
- Type: Anomaly
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2023-04-27
- Author: Teoderick Contreras, Splunk
- ID: 73a56508-1cf5-4df7-b8d9-5737fbdc27d2
Kill Chain Phase
- Actions On Objectives
- CIS 10
1 2 3 4 5 6 | tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Filesystem where Filesystem.action=deleted AND Filesystem.file_path IN ("/etc/ssh/*", "~/.ssh/*") by _time span=1h Filesystem.file_name Filesystem.file_path Filesystem.dest Filesystem.process_guid Filesystem.action | `drop_dm_object_name(Filesystem)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `linux_account_manipulation_of_ssh_config_and_keys_filter`
The SPL above uses the following Macros:
linux_account_manipulation_of_ssh_config_and_keys_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line 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 execute this command. Please update the filter macros to remove false positives.
Associated Analytic Story
|49.0||70||70||SSH Config and keys are deleted on $dest$ by Process GUID - $process_guid$|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 2