Linux Auditd At Application Execution

name: Linux Auditd At Application Execution
id: 9f306e0a-1c36-469e-8892-968ca12470dd
version: 10
creation_date: '2021-12-21'
modification_date: '2026-05-13'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
description: The following analytic detects the execution of the "At" application in Linux, which can be used by attackers to create persistence entries on a compromised host. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and parent process names associated with "at" or "atd". This activity is significant because the "At" application can be exploited to maintain unauthorized access or deliver additional malicious payloads. If confirmed malicious, this behavior could lead to data theft, ransomware attacks, or other severe consequences. Immediate investigation is required to determine the legitimacy of the execution and mitigate potential risks.
data_source:
    - Linux Auditd Syscall
search: |-
    `linux_auditd` type=SYSCALL comm IN ("at", "atd") OR exe IN ("/usr/bin/at","/usr/bin/atd") AND NOT (uid IN ("daemon"))
      | rename host as dest
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY comm exe syscall
           uid ppid pid
           dest
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `linux_auditd_at_application_execution_filter`
how_to_implement: To implement this detection, the process begins by ingesting auditd data, that consist SYSCALL, TYPE, EXECVE and PROCTITLE events, which captures command-line executions and process details on Unix/Linux systems. These logs should be ingested and processed using Splunk Add-on for Unix and Linux (https://splunkbase.splunk.com/app/833), which is essential for correctly parsing and categorizing the data. The next step involves normalizing the field names  to match the field names set by the Splunk Common Information Model (CIM) to ensure consistency across different data sources and enhance the efficiency of data modeling. This approach enables effective monitoring and detection of linux endpoints where auditd is deployed
known_false_positives: Administrator or network operator can use this application for automation purposes. Please update the filter macros to remove false positives.
references:
    - https://attack.mitre.org/techniques/T1053/001/
    - https://www.linkedin.com/pulse/getting-attacker-ip-address-from-malicious-linux-job-craig-rowland/
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: A SYSCALL - [$comm$] event was executed on host - [$dest$] to execute the "at" application.
analytic_story:
    - Scheduled Tasks
    - Linux Privilege Escalation
    - Linux Persistence Techniques
    - Linux Living Off The Land
    - Compromised Linux Host
asset_type: Endpoint
mitre_attack_id:
    - T1053.002
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint