Detection: Azure AD Authentication Failed During MFA Challenge

Updated Date: 2024-05-18 ID: e62c9c2e-bf51-4719-906c-3074618fcc1c Author: Mauricio Velazco, Gowthamaraj Rajendran, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies failed authentication attempts against an Azure AD tenant during the Multi-Factor Authentication (MFA) challenge, specifically flagged by error code 500121. It leverages Azure AD SignInLogs to detect these events. This activity is significant as it may indicate an adversary attempting to authenticate using compromised credentials on an account with MFA enabled. If confirmed malicious, this could suggest an ongoing effort to bypass MFA protections, potentially leading to unauthorized access and further compromise of the affected account.

Search

1 `azure_monitor_aad` category=SignInLogs properties.status.errorCode=500121 
2| rename properties.* as * 
3| stats count min(_time) as firstTime max(_time) as lastTime by user, src_ip, status.additionalDetails, appDisplayName, user_agent 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `azure_ad_authentication_failed_during_mfa_challenge_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Azure Active Directory	Azure	`'azure:monitor:aad'`	`'Azure AD'`	N/A

Macros Used

Name	Value
azure_monitor_aad	`sourcetype=azure:monitor:aad`
azure_ad_authentication_failed_during_mfa_challenge_filter	`search *`

azure_ad_authentication_failed_during_mfa_challenge_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
T1078	Valid Accounts	Defense Evasion
T1078.004	Cloud Accounts	Initial Access
T1621	Multi-Factor Authentication Request Generation	Persistence

KillChainPhase.DELIVERY

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

KillChainPhase.WEAPONIZATION

NistCategory.DE_CM

Cis18Value.CIS_10

APT29

APT18

APT28

APT29

APT33

APT39

APT41

Akira

Axiom

Carbanak

Chimera

Cinnamon Tempest

Dragonfly

FIN10

FIN4

FIN5

FIN6

FIN7

FIN8

Fox Kitten

GALLIUM

Ke3chang

LAPSUS$

Lazarus Group

Leviathan

OilRig

POLONIUM

PittyTiger

Sandworm Team

Silence

Silent Librarian

Suckfly

Threat Group-3390

Wizard Spider

menuPass

APT28

APT29

APT33

APT5

Ke3chang

LAPSUS$

APT29

LAPSUS$

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

You must install the latest version of Splunk Add-on for Microsoft Cloud Services from Splunkbase (https://splunkbase.splunk.com/app/3110/#/details). You must be ingesting Azure Active Directory events into your Splunk environment through an EventHub. This analytic was written to be used with the azure:monitor:aad sourcetype leveraging the SignInLogs log category.

Known False Positives

Legitimate users may miss to reply the MFA challenge within the time window or deny it by mistake.

Associated Analytic Story

Azure Active Directory Account Takeover

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
User $user$ failed to pass MFA challenge	54	60	90

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	`Azure AD`	`azure:monitor:aad`
Integration	✅ Passing	Dataset	`Azure AD`	`azure:monitor:aad`

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