AWS EC2 Startup Shell Script Change — Sigma Rule

Rule metadata and linked tags

Author: faloker. Source status: test; severity: high. Source dates: 2020-02-12 / 2022-06-07.

{
  "product": "aws",
  "service": "cloudtrail"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 8b58ce7431b1b3964cf0239c95164d92c9ce51c941101f70d901f7ff3b71b727

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: AWS EC2 Startup Shell Script Change
id: 1ab3c5ed-5baf-417b-bb6b-78ca33f6c3df
status: test
description: Detects changes to the EC2 instance startup script. The shell script will be executed as root/SYSTEM every time the specific instances are booted up.
references:
    - https://github.com/RhinoSecurityLabs/pacu/blob/866376cd711666c775bbfcde0524c817f2c5b181/pacu/modules/ec2__startup_shell_script/main.py#L9
author: faloker
date: 2020-02-12
modified: 2022-06-07
tags:
    - attack.execution
    - attack.t1059.001
    - attack.t1059.003
    - attack.t1059.004
logsource:
    product: aws
    service: cloudtrail
detection:
    selection_source:
        eventSource: ec2.amazonaws.com
        requestParameters.attribute: 'userData'
        eventName: ModifyInstanceAttribute
    condition: selection_source
falsepositives:
    - Valid changes to the startup script
level: high

Original YAML and metadata in JSON

False positives

• Valid changes to the startup script

Source references

• https://github.com/RhinoSecurityLabs/pacu/blob/866376cd711666c775bbfcde0524c817f2c5b181/pacu/modules/ec2__startup_shell_script/main.py#L9