Microsoft has announced that Microsoft 365 applications will soon block file access via the File Protocol Remote Procedure Call (FPRPC) legacy authentication protocol by default. FPRPC is an older protocol used by Microsoft 365 apps to access files remotely, but it has been identified as insecure due to its reliance on legacy authentication methods that are vulnerable to interception and misuse. By blocking FPRPC, Microsoft aims to reduce the attack surface associated with legacy authentication protocols that can be exploited for unauthorized file access or lateral movement within networks. This change is part of Microsoft's broader initiative to enhance security by deprecating legacy protocols and enforcing modern authentication standards. Although no known exploits are currently reported in the wild targeting this protocol, the move to block FPRPC by default indicates a proactive mitigation of potential vulnerabilities inherent in the protocol. The update will affect Microsoft 365 apps across environments where FPRPC is still enabled or used, potentially impacting workflows that depend on legacy file access methods. Organizations will need to ensure their environments are compatible with modern authentication protocols and update any dependent systems or scripts accordingly to avoid disruptions.

For European organizations, the blocking of FPRPC by default in Microsoft 365 apps will have several impacts. Firstly, organizations still relying on legacy authentication protocols for file access may experience service disruptions or failures in workflows that depend on FPRPC. This could affect productivity and require urgent remediation. Secondly, the security posture of organizations will improve by reducing exposure to legacy protocol vulnerabilities, which are often exploited in targeted attacks or ransomware campaigns. This is particularly relevant for sectors with high regulatory requirements such as finance, healthcare, and government institutions across Europe. Additionally, organizations with hybrid or complex Microsoft 365 deployments may need to audit and update their configurations to ensure compatibility with modern authentication methods, which could require resource allocation and technical expertise. Overall, while the change may cause short-term operational challenges, it significantly enhances long-term security by mitigating risks associated with legacy protocol exploitation.

European organizations should take the following specific steps to mitigate potential issues arising from this change: 1) Conduct a comprehensive audit of Microsoft 365 environments to identify any usage of FPRPC or legacy authentication protocols for file access. 2) Update or reconfigure applications, scripts, and workflows that rely on FPRPC to use supported modern authentication protocols such as OAuth 2.0 or Microsoft Graph API. 3) Engage with Microsoft 365 administrators and security teams to review conditional access policies and ensure legacy authentication is disabled where possible. 4) Test the impact of blocking FPRPC in controlled environments before the default enforcement to identify and remediate any compatibility issues. 5) Provide training and communication to IT staff and end-users about the change to prepare for potential disruptions and promote security best practices. 6) Monitor Microsoft 365 security advisories and update management tools to apply patches or configuration changes promptly. These targeted actions will help organizations transition smoothly and maintain secure, uninterrupted access to Microsoft 365 resources.