Problem Detected

So uh something seems to have gone wrong with my file.

I got a message this morning from my virus protection that a malicious attack had been blocked and it said it had something to do with my game demo file? 

I honestly have no idea what went wrong but a Trojan virus was found and I DON'T want anyone getting something like that because of my file, so I removed it for now. But I'm lost on this , I don't even know how a Trojan is made, does anyone know what I did wrong?