Which of the following statements about system hardening are true? Each correct answer represents a complete solution. Choose two.

Which of the following statements about system hardening are true? Each correct answer represents a complete solution. Choose two.
A . It can be achieved by installing service packs and security updates on a regular basis.
B . It is used for securing the computer hardware.
C . It can be achieved by locking the computer room.
D . It is used for securing an operating system.

Answer: AD