Detection: ASL AWS New MFA Method Registered For User

Updated Date: 2025-06-10 ID: 33ae0931-2a03-456b-b1d7-b016c5557fbd Author: Patrick Bareiss, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies the registration of a new Multi-Factor Authentication (MFA) method for an AWS account, as logged through Amazon Security Lake (ASL). It detects this activity by monitoring the CreateVirtualMFADevice API operation within ASL logs. This behavior 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 activity could allow attackers to secure their access, making it harder to detect and remove their presence from the compromised environment.

Search

1`amazon_security_lake` api.operation=CreateVirtualMFADevice 
2| fillnull 
3| stats count min(_time) as firstTime max(_time) as lastTime by actor.user.uid api.operation api.service.name http_request.user_agent src_endpoint.ip actor.user.account.uid cloud.provider cloud.region 
4| rename actor.user.uid as user api.operation as action api.service.name as dest http_request.user_agent as user_agent src_endpoint.ip as src actor.user.account.uid as vendor_account cloud.provider as vendor_product cloud.region as vendor_region 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `asl_aws_new_mfa_method_registered_for_user_filter`

Data Source

Name	Platform	Sourcetype	Source
ASL AWS CloudTrail	AWS	`'aws:asl'`	`'aws_asl'`

Macros Used

Name	Value
amazon_security_lake	`sourcetype=aws:asl`
asl_aws_new_mfa_method_registered_for_user_filter	`search *`

asl_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

The detection is based on Amazon Security Lake events from Amazon Web Services (AWS), which is a centralized data lake that provides security-related data from AWS services. To use this detection, you must ingest CloudTrail logs from Amazon Security Lake into Splunk. To run this search, ensure that you ingest events using the latest version of Splunk Add-on for Amazon Web Services (https://splunkbase.splunk.com/app/1876) or the Federated Analytics App.

Known False Positives

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

Associated Analytic Story

AWS Identity and Access Management Account Takeover

Risk Based Analytics (RBA)

Risk Message:

A new virtual device is added to user $user$

Risk Object	Risk Object Type	Risk Score	Threat Objects
user	user	64	src

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`aws_asl`	`aws:asl`
Integration	✅ Passing	Dataset	`aws_asl`	`aws:asl`

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: 10