If I downloaded an installation program (say a game or something) using uTorrent and scanned it with my antivirus program (I have Avast), could it still have a virus in its installation file when Avast said there were no virus's? Basically, my friends have been telling me that even if I scan an .exe file and no virus's are found, there could still be a virus in there when I install it. Is this true?

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I know my user name sounds lame. It was the first thing I could think of, but it seems to fit seeing as this is a computer help forum. ^__^
And you can of course change it if you wish.

Yes it could still have a virus (typically a spyware). You can make something Foolproof, but not damn foolproof. Nothing is perfect!!! Those damn fools keep messing it up!

Therefore, do NOT rely on your antivirus software. There is still a lag between when a virus is introduced and identified until there is a definition available for the scanner to use to block the problem. Also, in all the hard work to compile a list, some malware still sneaks through.