People don't hack into your computer just randomly, you must first have something they want and even then it is nearly impossible with a good virus scanner.
You are too paranoid indeed.
They want your computer for their botnet. Everyone is welcome for those... they just want your cpu/gpu/spamming IP resources.
Just use a good virus scanner like Avast! That one usually detects malware and just don't download files you think might be a virus.
People don't hack into your computer just randomly, you must first have something they want and even then it is nearly impossible with a good virus scanner.