Malicious Usage Of IMDS Credentials Outside Of AWS Infrastructure — Sigma Rule

Rule metadata and linked tags

Author: jamesc-grafana. Source status: test; severity: high. Source dates: 2024-07-11 / not supplied.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: b070399db57d212727d7f7873c642a0c1da0930c2b45a5fe8945c3e2474caf37

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: Malicious Usage Of IMDS Credentials Outside Of AWS Infrastructure
id: 352a918a-34d8-4882-8470-44830c507aa3
status: test
description: |
    Detects when an instance identity has taken an action that isn't inside SSM.
    This can indicate that a compromised EC2 instance is being used as a pivot point.
references:
    - https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-identity-roles.html
    - https://ermetic.com/blog/aws/aws-ec2-imds-what-you-need-to-know/
    - https://www.packetmischief.ca/2023/07/31/amazon-ec2-credential-exfiltration-how-it-happens-and-how-to-mitigate-it/#lifting-credentials-from-imds-this-is-why-we-cant-have-nice-things
author: jamesc-grafana
date: 2024-07-11
tags:
    - attack.privilege-escalation
    - attack.initial-access
    - attack.persistence
    - attack.stealth
    - attack.t1078
    - attack.t1078.002
logsource:
    product: aws
    service: cloudtrail
detection:
    selection:
        userIdentity.arn|re: '.+:assumed-role/aws:.+'
    filter_main_generic:
        - eventSource: 'ssm.amazonaws.com'
        - eventName: 'RegisterManagedInstance'
        - sourceIPAddress: 'AWS Internal'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - A team has configured an EC2 instance to use instance profiles that grant the option for the EC2 instance to talk to other AWS Services
level: high

Original YAML and metadata in JSON

False positives

• A team has configured an EC2 instance to use instance profiles that grant the option for the EC2 instance to talk to other AWS Services

Source references

• https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-identity-roles.html
• https://ermetic.com/blog/aws/aws-ec2-imds-what-you-need-to-know/
• https://www.packetmischief.ca/2023/07/31/amazon-ec2-credential-exfiltration-how-it-happens-and-how-to-mitigate-it/#lifting-credentials-from-imds-this-is-why-we-cant-have-nice-things