The Trojans, believing the horse to be some kind of gift, rolled the horse into the city. At that point, the Greeks exited the horse and killed the Trojans. In computer terms a Trojan horse is a program that masquerades as a legitimate program, but in reality harbors a program that could damage your files. A good virus detection program will detect and hopefully remove a virus or Trojan horse. Some important factors to consider when deciding on an AV program is efficiency, number of viruses detected, detection method, and ease of use.
Efficiency is a generic term that refers to the productivity of the AV program.
An efficient AV program will quickly scan your drive to locate and remove viruses without giving too many false alarms. One should be wary about statements that refer to the number of viruses that are detected. Unlike the PC world, where there are several thousand viruses, the Mac world has only a few hundred. Therefore, it more important for the AV program to detect all common viruses, rather than missing a common virus and detecting the 10 rarest virus strains. Ease of use is a catch-all phrase that includes ease of install, ease of installation, ease of virus detection and removal, and the ability to turn on and forget about the AV software.