Detection: ASL AWS Multi-Factor Authentication Disabled

Updated Date: 2024-05-22 ID: 4d2df5e0-1092-4817-88a8-79c7fa054668 Author: Patrick Bareiss, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects attempts to disable multi-factor authentication (MFA) for an AWS IAM user. It leverages Amazon Security Lake logs, specifically monitoring for DeleteVirtualMFADevice or DeactivateMFADevice API operations. This activity is significant as disabling MFA can indicate an adversary attempting to weaken account security to maintain persistence using a compromised account. If confirmed malicious, this action could allow attackers to retain access to the AWS environment without detection, potentially leading to unauthorized access to sensitive resources and prolonged compromise.

Search

1`amazon_security_lake` (api.operation=DeleteVirtualMFADevice OR api.operation=DeactivateMFADevice) 
2| fillnull 
3| stats count min(_time) as firstTime max(_time) as lastTime by api.operation actor.user.account_uid actor.user.uid http_request.user_agent src_endpoint.ip cloud.region 
4| rename actor.user.uid as user, src_endpoint.ip as src_ip, cloud.region as region, http_request.user_agent as user_agent, actor.user.account_uid as aws_account_id 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `asl_aws_multi_factor_authentication_disabled_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
N/A	N/A	N/A	N/A	N/A

Macros Used

Name	Value
amazon_security_lake	`sourcetype=aws:cloudtrail:lake`
asl_aws_multi_factor_authentication_disabled_filter	`search *`

asl_aws_multi_factor_authentication_disabled_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
T1586	Compromise Accounts	Resource Development
T1586.003	Cloud Accounts	Resource Development
T1621	Multi-Factor Authentication Request Generation	Credential Access
T1556	Modify Authentication Process	Credential Access
T1556.006	Multi-Factor Authentication	Defense Evasion

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

KillChainPhase.WEAPONIZATION

NistCategory.DE_CM

Cis18Value.CIS_10

APT29

LAPSUS$

Scattered Spider

FIN13

Scattered Spider

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

AWS Administrators may disable MFA but it is highly unlikely for this event to occur without prior notice to the company

Associated Analytic Story

AWS Identity and Access Management Account Takeover

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
User $user$ has disabled Multi-Factor authentication for AWS account $aws_account_id$	64	80	80

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

References

Detection Testing

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

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: 3