Detection: O365 Disable MFA

Updated Date: 2024-05-11 ID: c783dd98-c703-4252-9e8a-f19d9f5c949e Author: Rod Soto, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies instances where Multi-Factor Authentication (MFA) is disabled for a user within the Office 365 environment. It leverages O365 audit logs, specifically focusing on events related to MFA settings. Disabling MFA removes a critical security layer, making accounts more vulnerable to unauthorized access. If confirmed malicious, this activity could indicate an attacker attempting to maintain persistence or an insider threat, significantly increasing the risk of unauthorized access. Immediate investigation is required to validate the reason for disabling MFA, potentially re-enable it, and assess any other suspicious activities related to the affected account.

1`o365_management_activity` Operation="Disable Strong Authentication." 
2| stats count earliest(_time) as firstTime latest(_time) as lastTime by UserType Operation UserId ResultStatus object 
3| rename UserType AS user_type, Operation AS action, UserId AS src_user, object AS user, ResultStatus AS result 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `o365_disable_mfa_filter`

Data Source

Name Platform Sourcetype Source Supported App
O365 Disable Strong Authentication. N/A 'o365:management:activity' 'o365' N/A

Macros Used

Name Value
o365_management_activity sourcetype=o365:management:activity
o365_disable_mfa_filter search *
o365_disable_mfa_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 Modify Authentication Process Credential Access
KillChainPhase.EXPLOITAITON
KillChainPhase.INSTALLATION
NistCategory.DE_CM
Cis18Value.CIS_10
FIN13

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 Splunk Microsoft Office 365 add-on. This search works with o365:management:activity

Known False Positives

Unless it is a special case, it is uncommon to disable MFA or Strong Authentication

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
User $src_user$ has executed an operation $action$ for user $user$ 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 o365 o365:management:activity
Integration ✅ Passing Dataset o365 o365:management:activity

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