Detection rules › Sigma
Malicious Usage Of IMDS Credentials Outside Of AWS Infrastructure
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.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Initial Access | T1078.002 Valid Accounts: Domain Accounts |
| Persistence | T1078.002 Valid Accounts: Domain Accounts |
| Privilege Escalation | T1078.002 Valid Accounts: Domain Accounts |
| Stealth | T1078.002 Valid Accounts: Domain Accounts |
Event coverage
| Provider | Event |
|---|---|
| AWS-ssm | RegisterManagedInstance |
Rule body yaml
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
Stages and Predicates
Stage 0: condition
selection and not 1 of filter_main_*Stage 1: selection
selection:
userIdentity.arn|re: '.+:assumed-role/aws:.+'
Stage 2: not filter_main_generic
filter_main_generic:
- eventSource: 'ssm.amazonaws.com'
- eventName: 'RegisterManagedInstance'
- sourceIPAddress: 'AWS Internal'
Exclusions
Top-level NOT(...) conjuncts: predicates this rule actively suppresses.
| Field | Kind | Excluded values |
|---|---|---|
eventName | eq | RegisterManagedInstance |
eventSource | eq | ssm.amazonaws.com |
sourceIPAddress | eq | AWS Internal |
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
userIdentity.arn | regex_match |
|