What method should the security administrator configure on the VPN to implement two-factor authentication?

The most effective method for implementing two-factor authentication on a VPN is to use a combination of something you have and something you know. In this context, the best option involves introducing biometric verification as a second factor.

When configuring a VPN for two-factor authentication, the process typically involves requiring users to provide not just their standard credentials—such as a username and password—but also a second verification method. This second factor could be a time-sensitive code from a mobile app, a hardware token, or biometric verification, which adds a strong layer of security by ensuring that the individual attempting to connect to the VPN is indeed authorized.

Biometric verification, such as fingerprints or facial recognition, is particularly robust, as it is highly unique to the individual and difficult to replicate. This significantly reduces the risk of unauthorized access. In contrast, solely using a username and password (as indicated in one of the other choices) does not satisfy the two-factor requirement, as it only involves a single layer of authentication based on something the user knows.

In summary, using biometric verification as a second factor significantly enhances security by requiring users to verify their identities using a unique physical characteristic, making it the correct method for implementing two-factor authentication in a VPN setup.