Microsoft has announced plans to phase out the NTLM (New Technology LAN Manager) authentication protocol in Windows 11, aiming to enhance the security of the operating system. Despite being the default protocol for authentication in older Windows versions, NTLM has been extensively exploited by threat actors in various attacks, such as NTLM relay attacks and pass-the-hash attacks.
In response, Microsoft has introduced new Kerberos features, including IAKerb and Local KDC (Key Distribution Center), to improve security and provide broader network authentication support, even for local user accounts.
The decision to move away from NTLM is based on the superior security provided by the Kerberos authentication protocol, which has become the default authentication protocol for domain-connected devices in modern Windows versions. NTLM’s vulnerabilities have been leveraged by malicious actors in attacks that compromise network devices and elevate privileges, gaining control over Windows domains. The introduction of the two Kerberos features aims to combat challenges leading to Kerberos fallback to NTLM, ensuring a more secure environment for Windows 11 users.
Microsoft advises developers to discontinue the use of NTLM in their applications and has recommended Windows administrators disable NTLM or implement measures to block NTLM relay attacks. The phased reduction of NTLM usage and the expansion of management controls offer administrators greater flexibility in monitoring and restricting NTLM within their environments.
Eventually, Microsoft plans to disable NTLM by default in Windows 11, but customers will still have the option to reenable it for compatibility reasons. This strategic shift underscores Microsoft’s commitment to enhancing the security and integrity of its operating system.