Microsoft has announced that Microsoft 365 apps for Windows will block access via the insecure FPRPC protocol by default from the end of August 2025. The change is intended to increase security by reducing exposure to outdated technologies.
The step follows an earlier announcement in June. At that time, Microsoft announced that it would update the security standards for all Microsoft 365 tenants to prevent file access via outdated authentication protocols such as RPS and FPRPC.
Since the beginning of this year, Microsoft has implemented several security measures. All ActiveX controls in Windows versions of Microsoft 365 and Office 2024 apps have been disabled. A new Teams feature was also announced that blocks screenshots during meetings.
Microsoft recently expanded the list of blocked Outlook attachments to include .library-ms and .search-ms file types. These measures are aimed at protecting users from brute-force attacks and phishing via outdated authentication methods.
New management options
Microsoft is introducing new Trust Center settings that allow users to re-enable FPRPC if desired. However, this only applies if the feature is not managed by Group Policy or the Cloud Policy Service (CPS). In addition, users can disable FTP and HTTP files, although these protocols remain allowed by default.
Administrators can control authentication protocol settings via the Cloud Policy Service under Microsoft 365 Apps settings. When a protocol is disabled via CPS, users can no longer enable it via the Trust Center.
Starting with version 2508 of Microsoft 365 apps, files that use the FPRPC protocol will be automatically blocked. Instead, a more secure fallback protocol will open the files. The changes will be generally available starting in late August 2025, with expected implementation for all tenants by the end of September.
The block specifically targets Microsoft 365 apps for Windows. Users of Microsoft Teams on Windows, Mac, web, iOS, or Android will not be affected by these changes.
Tip: Old technology is being phased out of Windows and Microsoft 365