A company has a remote access VPN and wants to ensure that if a username and password are compromised, the corporate network will remain secure. Which of the following will allow the company to…

Posture assessment evaluates the security health of a device before granting VPN access - it checks for things like antivirus status but does not prevent access when valid credentials are used.

Kerberos is a network authentication protocol that issues tickets - it still relies on the initial username and password and does not by itself add a second factor.

TACACS+ is a AAA protocol used for centralized authentication, authorization, and accounting - it can facilitate 2FA but is not itself a two-factor mechanism.

Two-factor authentication combines something the user knows (password) with something the user has or is (token, smart card, biometric), so even if a username and password are stolen, an attacker cannot authenticate without also possessing the second factor, directly addressing the threat scenario described.