As the other responders suggest, people don't practice safe computing.  Anti-virus, anti-spyware, firewall...all good and necessary.\n\nStill, most of us think that if we have the software (or hardware) protecting us, then we must be completely safe and we can go happily on our merry way.  I assure you, this is a false sense of security.  Do not trust the hardware or software to do the whole job for you.\n\nI believe the primary reason why computers get a virus is a lack of common sense.  To wit...\n- Be skeptical of anything you receive in e-mail that was not solicited, especially if it has an attachment.\n- Think twice before downloading that freeware.\n- Avoid Kazaa and the like.\n- Do review website certificates to satisfy yourself that the site you're heading for is really the site you wanted to go to.\n- Make sure you download and install every security patch your OS vendor provides.  You should manually review your vendor at least weekly...even if you have an automatic update feature.\n\nA few minutes spent on satisfying yourself that you've done everything you can do will provide you with peace of mind.
what is the main cause why computer gets a virus?