Remove Scheduled Cron Task/Job

Status: test
Severity: medium
Log source: category process_creation, product linux
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects usage of the 'crontab' utility to remove the current crontab. This is a common occurrence where cryptocurrency miners compete against each other by removing traces of other miners to hijack the maximum amount of resources possible

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	No specific technique

Telemetry coverage

Platform	Record / event type
Linux	Event ID 1: Process Create

Rule body

title: Remove Scheduled Cron Task/Job
id: c2e234de-03a3-41e1-b39a-1e56dc17ba67
status: test
description: |
    Detects usage of the 'crontab' utility to remove the current crontab.
    This is a common occurrence where cryptocurrency miners compete against each other by removing traces of other miners to hijack the maximum amount of resources possible
references:
    - https://www.trendmicro.com/en_us/research/22/i/how-malicious-actors-abuse-native-linux-tools-in-their-attacks.html
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-09-15
tags:
    - attack.stealth
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: 'crontab'
        CommandLine|contains: ' -r'
    condition: selection
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    Image|endswith: 'crontab'
    CommandLine|contains: ' -r'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`-r`	`field:"CommandLine" kind:match value:" -r"`
`Image`	ends_with	`crontab`	`field:"Image" kind:ends_with value:"crontab"`