Trojan horse attacks pose one of the most serious threats to computer security. The image below shows different ways a Trojan can get into a system. Which are the easiest and most convincing ways to infect a computer?

A.
IRC (Internet Relay Chat)

B.
Legitimate “shrink-wrapped” software packaged by a disgruntled employee

C.
NetBIOS (File Sharing)

D.
Downloading files, games and screensavers from Internet sites