Try in Splunk Security Cloud

Description

The following analytic identifies a suspicious file creation of /etc/at.allow or /etc/at.deny. These 2 files are commonly abused by malware, adversaries or red teamers to persist on the targeted or compromised host. These config files can restrict or allow user to execute "at" application (another schedule task application in linux). attacker can create a user or add the compromised username to that config file to execute "at" to schedule it malicious code. This anomaly detection can be a good indicator to investigate further the entry in created config file and who created it to verify if it is a false positive.

  • Type: Anomaly
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2021-12-17
  • Author: Teoderick Contreras, Splunk
  • ID: 977b3082-5f3d-11ec-b954-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1053.003 Cron Execution, Persistence, Privilege Escalation
T1053 Scheduled Task/Job Execution, Persistence, Privilege Escalation
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE 


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.file_path IN ("*/etc/at.allow", "*/etc/at.deny") by Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.process_guid Filesystem.file_path 
| `drop_dm_object_name(Filesystem)` 
| `security_content_ctime(lastTime)` 
| `security_content_ctime(firstTime)` 
| `linux_at_allow_config_file_creation_filter`

Macros

The SPL above uses the following Macros:

:information_source: linux_at_allow_config_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 into the Endpoint datamodel. 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 this file for automation purposes. Please update the filter macros to remove false positives.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
25.0 50 50 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

source | version: 1