Which of the following authentication methods prevents unauthorized execution of code on remote
systems?

A.
TACACS

B.
S-RPC

C.
RADIUS

D.
CHAP

Explanation:
Secure RPC (Remote Procedure Call) is an authentication method used to authenticate
the user and the host. It also prevents unauthorized
execution of code on remote systems. S-RPC uses the Diffie-Hellman and DES mechanisms. It is
required for the applications to have the NFS
and the NIS+ name service if they use Secure RPC.
Answer option C is incorrect. Remote Authentication Dial In User Service (RADIUS) is a networking
protocol that provides centralized access,
authorization and accounting management for people or computers to connect and use a network
service. When a person or device connects

to a network often authentication is required. RADIUS is commonly used by ISPs and corporations
managing access to the Internet or internal
networks employing a variety of networking technologies, including modems, DSL, wireless and
VPNs.
Answer option A is incorrect. Terminal Access Controller Access-Control System (TACACS) is a
remote authentication protocol that is used to
communicate with an authentication server commonly used in UNIX networks. TACACS allows a
remote access server to communicate with an
authentication server in order to determine if the user has access to the network. TACACS allows a
client to accept a username and password
and send a query to a TACACS authentication server, sometimes called a TACACS daemon. It uses
UDP port 49 as the default port.
Answer option D is incorrect. Challenge Handshake Authentication Protocol (CHAP) is an
authentication protocol that uses a secure form of
encrypted authentication. Using CHAP, network dial-up connections are able to securely connect to
almost all PPP servers.