Exam CISSP topic 1 question 114 discussion

The answer is D. SSO does not required additional authentication or verification.

The MOST effective method to enhance the security of a single sign-on (SSO) solution that interfaces with critical systems is: A. Two-factor authentication Two-factor authentication (2FA) adds an additional layer of security to the authentication process by requiring users to provide two forms of identification: something they know (e.g., a password) and something they have (e.g., a physical token or a mobile device). This approach significantly reduces the risk of unauthorized access even if the user's password is compromised.

A. Once you're in sso you can go anywhere without prompts, that's the whole point. So the security is up front at login, MFA is a great way to increase security. Everything should be ssl/tls too.

SSO with Two Factor Authentication is common

You may enable SS/TLS, but if an attacker already knows the password then what's the point?

B and C are easily eliminated A and D both sound right. But A could be right considering the keyword "enhance" - I would assume SSL is already in place for securing data to/ from critical systems. So, validating user authentication with multi-factor sounds right.