The most common of all these computer viruses are: Trojan Horses, Worms, Boot sector Virus, Macro virus, Memory Resident Viruses, Root kit Virus, Polymorphic viruses, and last Logic/Time Bombs, and here are how they all work. Trojan horses program appears to be helpful and has qualities that are desired. Once you have downloaded this software or program it may tell you of the work it has been doing on you computer but it will also be secretly performing other undesired effects. The Trojan horse does not replicate itself but does damage your computer. A Trojan horse is sent by either an advertisement to download a software