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MediumSplunk security contentBhavin Patel +2

O365 Bypass MFA via Trusted IP

The following analytic identifies instances where new IP addresses are added to the trusted IPs list in Office 365, potentially allowing users from these IPs to bypass Multi-Factor Authentication (MFA) during login.…

Description

The following analytic identifies instances where new IP addresses are added to the trusted IPs list in Office 365, potentially allowing users from these IPs to bypass Multi-Factor Authentication (MFA) during login. It leverages O365 audit logs, specifically focusing on events related to the modification of trusted IP settings. This activity is significant because adding trusted IPs can weaken the security posture by bypassing MFA, which is a critical security control. If confirmed malicious, this could lead to unauthorized access, compromising sensitive information and systems. Immediate investigation is required to validate the legitimacy of the IP addition.

Detection logic

Detection requirements

Platform
IaaS

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
o365_set_company_information

Known benign triggers

  • Unless it is a special case, it is uncommon to continually update Trusted IPs to MFA configuration.

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