Preventing Unauthorized Code Execution

B.

The authentication method that prevents unauthorized execution of code on remote systems is D. CHAP (Challenge Handshake Authentication Protocol).

CHAP is a mutual authentication protocol that is used to authenticate remote users or systems. It works by using a three-way handshake process between the client and the server. During this process, the client sends an initial request to the server to authenticate, and the server responds by challenging the client to prove its identity.

The challenge is typically a random string of characters, which the client must use to create a response. The response is generated by running a one-way hash function on the challenge and a shared secret, which is known only to the client and the server. The response is sent back to the server, which checks it against its own calculation. If the response is correct, the server grants access to the client.

By using CHAP, remote systems can be sure that the user or system is who they claim to be, and that they have not been compromised by unauthorized code execution. CHAP is a more secure authentication method than many other types, such as PAP (Password Authentication Protocol), which transmits passwords in plaintext and is therefore more vulnerable to interception and eavesdropping.

TACACS (Terminal Access Controller Access Control System), RADIUS (Remote Authentication Dial-In User Service), and S-RPC (Secure Remote Procedure Call) are also authentication methods, but they do not provide the same level of protection against unauthorized code execution as CHAP. TACACS and RADIUS are primarily used for network access control, while S-RPC is a protocol that allows remote execution of procedures on a server.