Detection: AWS New MFA Method Registered For User

Updated Date: 2025-02-10 ID: 4e3c26f2-4fb9-4bd7-ab46-1b76ffa2a23b Author: Bhavin Patel, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the registration of a new Multi-Factor Authentication (MFA) method for an AWS account. It leverages AWS CloudTrail logs to identify the CreateVirtualMFADevice event. This activity is significant because adversaries who gain unauthorized access to an AWS account may register a new MFA method to maintain persistence. If confirmed malicious, this could allow attackers to secure their access, making it difficult to detect and remove their presence, potentially leading to further unauthorized activities and data breaches.

1`cloudtrail` eventName=CreateVirtualMFADevice 
2| stats count values(requestParameters.virtualMFADeviceName) as virtualMFADeviceName min(_time) as firstTime max(_time) as lastTime by eventSource aws_account_id errorCode userAgent eventID awsRegion userIdentity.principalId user_arn src_ip 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `aws_new_mfa_method_registered_for_user_filter`

Data Source

Name Platform Sourcetype Source
AWS CloudTrail CreateVirtualMFADevice AWS icon AWS 'aws:cloudtrail' 'aws_cloudtrail'

Macros Used

Name Value
cloudtrail sourcetype=aws:cloudtrail
aws_new_mfa_method_registered_for_user_filter search *
aws_new_mfa_method_registered_for_user_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK
+ Kill Chain Phases
+ NIST
+ CIS
- Threat Actors
ID Technique Tactic
T1556.006 Multi-Factor Authentication Credential Access
Exploitation
Installation
DE.CM
CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting Value
Disabled true
Cron Schedule 0 * * * *
Earliest Time -70m@m
Latest Time -10m@m
Schedule Window auto
Creates Notable Yes
Rule Title %name%
Rule Description %description%
Notable Event Fields user, dest
Creates Risk Event True
This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

You must install Splunk AWS add on and Splunk App for AWS. This search works when AWS CloudTrail logs.

Known False Positives

Newly onboarded users who are registering an MFA method for the first time will also trigger this detection.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message:

A new virtual device $virtualMFADeviceName$ is added to user $user_arn$

Risk Object Risk Object Type Risk Score Threat Objects
user_arn user 64 src_ip

References

Detection Testing

Test Type Status Dataset Source Sourcetype
Validation ✅ Passing N/A N/A N/A
Unit ✅ Passing Dataset aws_cloudtrail aws:cloudtrail
Integration ✅ Passing Dataset aws_cloudtrail aws:cloudtrail

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 6