Which of the following is related to network security?

A firewall protects a network by filtering and controlling incoming and outgoing traffic.

Worms are self replicating malware that spread and harm systems.

Keyloggers are spyware that secretly record a user's keystrokes.

A Trojan is malware disguised as legitimate software to gain entry.

A firewall is a protective barrier, while the other three are security threats.

Firewalls can be hardware based, software based or a combination of both.