Which security measure helps to prevent unauthorized access by requiring a user to enter a specific code to gain entry?

Password protection is a critical security measure that helps prevent unauthorized access by requiring users to enter a specific code, which is their password, in order to gain access to a system or application. This method is effective because it ensures that only individuals who know the correct password can enter the system, thus adding a layer of security. Passwords act as a barrier against unauthorized users and can be designed to be complex enough to deter guessing or brute-force attacks.

Strong password practices may also involve regular changes to the password, the use of multifactor authentication, or the implementation of non-guessable passwords. This multifaceted approach strengthens the overall security posture of the system or data being protected.

The other options offered are important security measures as well, but they serve different functions. Encryption protects data by converting it into an unreadable format unless decrypted with the correct key, which does not directly involve user input for access. Firewalls act as a barrier to control incoming and outgoing network traffic based on predetermined security rules, and physical barriers involve tangible security means, like locks or fences, to prevent unauthorized physical access to a location. While all these measures contribute to a comprehensive security strategy, password protection specifically requires user interaction to gain access, making it the correct answer in this case