"Access to Microsoft SharePoint Online is monitored" when browsing to a SharePoint site

Symptoms

When users browse to a Microsoft SharePoint site or OneDrive site, they're redirected to the https://tenant-onmicrosoft.com.nas002.access-control.cas.ms/aad_login page. Additionally, they receive a warning message that resembles the following:

Access to Microsoft SharePoint Online is monitored.

For improved security, your organization allows access to Microsoft SharePoint Online in monitor mode. Access is only available from a web browser. Continue to Microsoft SharePoint Online

After they click the "Continue to Microsoft SharePoint Online" link, they're redirected again to a site that resembles the following:

https://tenant.sharepoint.com.us2.case.ms/sitepages/home.aspx

Cause

This issue occurs if a Microsoft Defender for Cloud Apps policy applies to the user's session.

Note

When you create a session policy, each user session that matches the policy is redirected to session control instead of to the app directly. For example, if the app returns a page that uses links whose domains end in myapp.com, Conditional Access Web App Control replaces the links with domains that end in something that resembles myapp.com.us.cas.ms. In this case, all the sessions are monitored by Microsoft Defender for Cloud Apps.

Resolution

If you don't want to notify users that they're being monitored, you can disable the notification message. To do this, follow these steps:

  1. Select the Settings icon (cog), and then select General settings.
  2. Under Conditional Access App Control, select User monitoring, and then clear the Notify users check box.

To keep users within the session, Conditional Access Web App Control replaces all the relevant URLs, Java scripts, and cookies within the app session with Microsoft Defender for Cloud Apps URLs.

To disable monitoring, you have to browse to the Microsoft Defender for Cloud Apps page, select the activity log, and then search for the affected users. After you locate the policy, you can either disable the policy or remove the users from the group so that the policy no longer affects them.

More information

For more information, see Session policies.

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