name: Linux At Application Execution
id: bf0a378e-5f3c-11ec-a6de-acde48001122
version: 2
date: '2022-05-26'
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. The "At" application can be used for automation purposes by administrators
  or network operators, so the filter macros should be updated to remove false positives.
  If a true positive is found, it suggests an attacker is trying to maintain access
  to the environment or potentially deliver additional malicious payloads, leading
  to data theft, ransomware, or other damaging outcomes. To implement this analytic,
  ensure you are ingesting logs with the required fields from your endpoints into
  the Endpoint datamodel. When a true positive is detected, it suggests that an attacker
  is attempting to establish persistence or deliver additional malicious payloads
  by leveraging the "At" application. This behavior can lead to data theft, ransomware
  attacks, or other damaging outcomes.\

  During triage, the SOC analyst should review the context surrounding the execution
  of the "At" application. This includes identifying the user, the parent process
  responsible for invoking the application, and the specific command-line arguments
  used. It is important to consider whether the execution is expected behavior by
  an administrator or network operator for legitimate automation purposes.\

  The presence of "At" application execution may indicate an attacker''s attempt to
  maintain unauthorized access to the environment. Immediate investigation and response
  are necessary to mitigate further risks, identify the attacker''s intentions, and
  prevent potential harm to the organization.'
data_source:
- Sysmon Event ID 1
search: '| tstats `security_content_summariesonly` count from datamodel=Endpoint.Processes
  where  Processes.process_name IN ("at", "atd") OR Processes.parent_process_name
  IN ("at", "atd") by Processes.dest Processes.user Processes.parent_process_name
  Processes.process_name Processes.process Processes.process_id Processes.parent_process_id
  Processes.process_guid | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)`
  | `security_content_ctime(lastTime)` | `linux_at_application_execution_filter`'
how_to_implement: The detection is based on data that originates from Endpoint Detection
  and Response (EDR) agents. These agents are designed to provide security-related
  telemetry from the endpoints where the agent is installed. To implement this search,
  you must ingest logs that contain the process GUID, process name, and parent process.
  Additionally, you must ingest complete command-line executions. These logs must
  be processed using the appropriate Splunk Technology Add-ons that are specific to
  the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint`
  data model. Use the Splunk Common Information Model (CIM) to normalize the field
  names and speed up the data modeling process.
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/
tags:
  analytic_story:
  - Linux Privilege Escalation
  - Linux Persistence Techniques
  - Linux Living Off The Land
  - Scheduled Tasks
  asset_type: Endpoint
  confidence: 30
  impact: 30
  message: At application was executed in $dest$
  mitre_attack_id:
  - T1053.002
  - T1053
  observable:
  - name: dest
    type: Hostname
    role:
    - Victim
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Processes.dest
  - Processes.user
  - Processes.parent_process_name
  - Processes.process_name
  - Processes.process
  - Processes.process_id
  - Processes.parent_process_id
  risk_score: 9
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1053.002/at_execution/sysmon_linux.log
    source: Syslog:Linux-Sysmon/Operational
    sourcetype: sysmon_linux