Viruses in General View to Protect your self

In 1989 when articles talked about first computer viruses, many poeple even programmers, thoulght this was a rumour, or a science-fiction story, but this was a fact and was expending band conquering the hole "world", and now it's a gr8 danger, in 1989 virusses can be counted on ur hand's fingers but now it passes 15000 virus, and variety of viruses make poeple worry:but why do poeple write viruses?
1-the first virus created =Brain also named pakistani:it was maded in pakistan, as a copyright for the writer programs
2-Stoned the stolen virus:a high school student wrote it, but his roomate stoll it and used it to destroy his frnds machines
3-some hackers looks at it, as a challenge, and...u know....who is the best keyboard cowboy???like the virus V2P and Mark Washburn, to prove tht , scanner type antiviruses, can't detect those viruses
4-Some fired programmers looking for revenge, those viruses can be described as atomic time bomb....yep
5-And Sure, and wich is totally unhuman and totally nonenoble:to encourage poeple to buy antiviruses,well here i totally support, antiviruses crackers, to give us free versions, an eye for an eye, a tooth for a tooth, but the first is evil
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well scientificly, a virus definition is:a very littel living entity unable to multiply but it has a powerful ADN to get inside a Cellul and make it produce more virusessame thing for computers viruses, they change a program(HOST) to produce more viruses.we can describe viruses as Replication able...tht's the diffrence btw. viruses and trojan/bombs...where worms are auto-fonctional

I-viruses:
a virus can't infect ur pc,only if u open it, then it enter the activity phase, note: dnt mess with a virus...viruses infect only macro and executable files

II-trojan horsesalso named patches (not evry thing named patch is a trojan ) it usually send files from the machine to the hacker(the trojan sender)

III-worms:
well worms copy it self, runs by it self, going into networks by it self....

IV-viruses mechanism types:
1-Replication:
it the copy phase without it the program is not called a virus
2-the protection mechanism:
also called sleath mechanism, it allows the virus to encode it self to be indetectble by antiviruses scanners
3-activate:
some viruses r timed, wich means, the virus is encoded, at a specified time it decodes it self then attacks, like MICHELANGELO virus which is activated every 6/avril , taiwan is a virus tht format the compuer after 90 reboot,and the manchu virus tht is activated by ctrl+alt+delete.
the only thing i can tell u when ur computer is infected,is the virus has "terminate and stay resident, TSR" then u r in big troubles.
well hope this will helps u not activating ur dark side