My virus scan is OS deep, I use a Mac
Honestly, before I switched I found that the performance degradation that came with continuous virus scanning on Windows was worse than most viruses.
It is. My mom is like "Why don't you have a virus scan?" on her 8 year old computer. I explained that the scanning made the computer unusable, so I used some free stuff every 3 months at night and get anything, there was never anything big, then delete it.
Norton fucked the computer up so badly that it wouldn't let me uninstall it and Windows had to be reinstalled.