AWS STS AssumeRole with New MFA Device

Identifies when a user has assumed a role using a new MFA device. Users can assume a role to obtain temporary credentials and access AWS resources using the AssumeRole API of AWS Security Token Service (STS). While a new MFA device is not always indicative of malicious behavior it should be verified as adversaries can use this technique for persistence and privilege escalation.

Rule type: new_terms

Rule indices:

filebeat-*
logs-aws.cloudtrail-*

Severity: low

Risk score: 21

Runs every: 5m

Searches indices from: None (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: Identity and Access Audit
Tactic: Privilege Escalation
Tactic: Persistence
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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event.dataset:aws.cloudtrail
    and event.provider:sts.amazonaws.com
    and event.action:(AssumeRole or AssumeRoleWithSAML or AssumeRoleWithWebIdentity)
    and event.outcome:success
    and user.id:*
    and aws.cloudtrail.flattened.request_parameters.serialNumber:*

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Modify Authentication Process
- ID: T1556
- Reference URL: https://attack.mitre.org/techniques/T1556/
Sub-technique:
- Name: Multi-Factor Authentication
- ID: T1556.006
- Reference URL: https://attack.mitre.org/techniques/T1556/006/
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/

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