But probably the most inexpensive full-blown solution comes from Moosoft, which specializes in solutions to Trojan horse programs.

CNN: Back Orifice 2000 under control

When word leaked out about a week ago that Sony was using a copy-protection program to keep people from copying their music CDs, music lovers cried foul and security experts warned the XCP copy protection system could be hijacked by so-called Trojan horse programs.

FORBES: Stringer's Sony Suspends Anti-Piracy CD Software

And even though Microsoft has a feature in its Internet Explorer browser designed to steer users away from unknown and potentially untrustworthy software, about 5 percent of users ignore the warnings and download malicious Trojan horse programs anyway. via Microsoft: One in 14 downloads is malicious.

FORBES: Users on Self-Destruct! Make 'em Pay!