---
title: "Linux At Allow Config File Creation"
excerpt: "Cron, Scheduled Task/Job"
categories:
  - Endpoint
last_modified_at: 2021-12-17
toc: true
toc_label: ""
tags:
  - Cron
  - Execution
  - Persistence
  - Privilege Escalation
  - Scheduled Task/Job
  - Execution
  - Persistence
  - Privilege Escalation
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  - Endpoint
---



[Try in Splunk Security Cloud](https://www.splunk.com/en_us/cyber-security.html){: .btn .btn--success}

#### 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 &#34;at&#34; application (another schedule task application in linux). attacker can create a user or add the compromised username to that config file to execute &#34;at&#34; 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](https://github.com/splunk/security_content/wiki/Detection-Analytic-Types)
- **Product**: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- **Datamodel**: [Endpoint](https://docs.splunk.com/Documentation/CIM/latest/User/Endpoint)
- **Last Updated**: 2021-12-17
- **Author**: Teoderick Contreras, Splunk
- **ID**: 977b3082-5f3d-11ec-b954-acde48001122


#### [ATT&CK](https://attack.mitre.org/)

| ID             | Technique        |  Tactic             |
| -------------- | ---------------- |-------------------- |
| [T1053.003](https://attack.mitre.org/techniques/T1053/003/) | Cron | Execution, Persistence, Privilege Escalation |

| [T1053](https://attack.mitre.org/techniques/T1053/) | Scheduled Task/Job | Execution, Persistence, Privilege Escalation |

#### Search

```

| 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:
* [security_content_ctime](https://github.com/splunk/security_content/blob/develop/macros/security_content_ctime.yml)
* [security_content_summariesonly](https://github.com/splunk/security_content/blob/develop/macros/security_content_summariesonly.yml)

Note that `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 field
* _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 this file for automation purposes. Please update the filter macros to remove false positives.

#### Associated Analytic story
* [Linux Privilege Escalation](/stories/linux_privilege_escalation)
* [Linux Persistence Techniques](/stories/linux_persistence_techniques)


#### Kill Chain Phase
* Privilege Escalation



#### RBA

| Risk Score  | Impact      | Confidence   | Message      |
| ----------- | ----------- |--------------|--------------|
| 25.0 | 50 | 50 | A file $file_name$ is created in $file_path$ on $dest$ |


Note that risk score is calculated base on the following formula: `(Impact * Confidence)/100`



#### Reference

* [https://linuxize.com/post/at-command-in-linux/](https://linuxize.com/post/at-command-in-linux/)



#### Test Dataset
Replay any dataset to Splunk Enterprise by using our [`replay.py`](https://github.com/splunk/attack_data#using-replaypy) tool or the [UI](https://github.com/splunk/attack_data#using-ui).
Alternatively you can replay a dataset into a [Splunk Attack Range](https://github.com/splunk/attack_range#replay-dumps-into-attack-range-splunk-server)

* [https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1053.001/at_execution/sysmon_linux.log](https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1053.001/at_execution/sysmon_linux.log)



[*source*](https://github.com/splunk/security_content/tree/develop/detections/endpoint/linux_at_allow_config_file_creation.yml) \| *version*: **1**