AWS STS Role Chaining

Identifies role chaining activity. Role chaining is when you use one assumed role to assume a second role through the AWS CLI or API. While this a recognized functionality in AWS, role chaining can be abused for privilege escalation if the subsequent assumed role provides additional privileges. Role chaining can also be used as a persistence mechanism as each AssumeRole action results in a refreshed session token with a 1 hour maximum duration. This rule looks for role chaining activity happening within a single account, to eliminate false positives produced by common cross-account behavior.

Rule type: esql

Rule indices: None

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-6m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Domain: Cloud
Data Source: AWS
Data Source: Amazon Web Services
Data Source: AWS STS
Use Case: Threat Detection
Tactic: Persistence
Tactic: Privilege Escalation
Tactic: Lateral Movement

Version: 1

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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Setup

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The AWS Fleet integration, Filebeat module, or similarly structured data is required to be compatible with this rule.

Rule query

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from logs-aws.cloudtrail-* metadata _id, _version, _index

// filter for AssumeRole API calls where access key id is a short term token beginning with ASIA
| where event.dataset == "aws.cloudtrail" and event.provider == "sts.amazonaws.com" and event.action == "AssumeRole" and aws.cloudtrail.resources.account_id == aws.cloudtrail.recipient_account_id and aws.cloudtrail.user_identity.access_key_id like "ASIA*"

// keep only the relevant fields
| keep aws.cloudtrail.user_identity.arn, cloud.region, aws.cloudtrail.resources.account_id, aws.cloudtrail.recipient_account_id, aws.cloudtrail.user_identity.access_key_id

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Privilege Escalation
- ID: TA0004
- Reference URL: https://attack.mitre.org/tactics/TA0004/
Technique:
- Name: Abuse Elevation Control Mechanism
- ID: T1548
- Reference URL: https://attack.mitre.org/techniques/T1548/
Tactic:
- Name: Lateral Movement
- ID: TA0008
- Reference URL: https://attack.mitre.org/tactics/TA0008/
Technique:
- Name: Use Alternate Authentication Material
- ID: T1550
- Reference URL: https://attack.mitre.org/techniques/T1550/
Sub-technique:
- Name: Application Access Token
- ID: T1550.001
- Reference URL: https://attack.mitre.org/techniques/T1550/001/
Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/

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