Which method of authentication is described as insecure within AC.L2-3.1.17?

The method of authentication described as insecure in the context of AC.L2-3.1.17 is Open authentication. Open authentication allows users to access a network or system without any form of credential validation, meaning that the system does not require any passwords or additional verification to grant access. This lack of security makes it vulnerable to unauthorized access, as it does not reliably ensure that the individual attempting to connect is indeed who they claim to be.

In contrast, RADIUS authentication, secure password authentication, and two-factor authentication all incorporate measures that enhance security. RADIUS is a protocol that provides centralized Authentication, Authorization, and Accounting, typically requiring valid credentials. Secure password authentication emphasizes the use of strong passwords to limit access. Two-factor authentication adds an additional layer of security beyond just a password, requiring users to provide a second form of verification, further mitigating the risk of unauthorized access.

The designation of Open authentication as insecure in the CMMC guidelines underscores the importance of implementing robust security practices to protect sensitive information and systems from potential threats.