# Authenticator Registration Anomalies

Detects when a user has registered a new authentication device with an operating system (OS) that differs from the previous authentication device's operating system, which may indicate malicious intent. A new authentication device that has a different OS type (iOS vs Android), an older OS version, and/or an OS that is unknown or unusual (non iOS/Android/Windows OS, etc) will lead to a user failing this check.

New accounts created in the last grace period of 7 days will not be evaluated against this check.

Attackers will often enroll authentication devices that are in their possession on the compromised end user's account to successfully pass potential MFA controls.

In some cases, MFA self-enrollment processes may require only a username and password to enroll the account's first device or to enroll an authentication device on an inactive account, making it easy for attackers to take over and control an end user account and retain access your environment.

**Recommended Actions**

Please verify the origin and nature of this authentication registration with the end user.

If the events do not appear to be from the appropriate end user, kill the sessions, remove the device as an allowed factor and take other remediation measures as necessary to keep the attacker from re-enabling the device or accessing the account again.

**Default Check Settings**

Grace period for new accounts (days): 7

**Compatibility**

[Duo](/integrations/duo-security-integration.md)

[Microsoft Entra ID](/integrations/azure-active-directory-integration.md)

[Okta](/integrations/okta-data-integration.md)

<figure><img src="/files/4B5pmLMIq5it1ChrREGk" alt=""><figcaption></figcaption></figure>


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