Which of the following is by far the most common prevention system from a network security
perspective?

A.
Firewall

B.
IDS

C.
IPS

D.
Hardened OS

E.
Tripwire

F.
None of the choices.

Explanation:
User account access controls and cryptography can protect systems files and data, respectively.
On the other hand, firewalls are by far the most common prevention systems from a network
security perspective as they can shield access to internal network services, and block certain kinds
of attacks through packet filtering.