I have used Norton security for long time. later I removed Norton and installed MSE(Microsoft security essentials, which is now a part of windows 10 windows defender so I don’t need any antivirus anymore) and on scan I found there were few viruses and harmful files in my PC which Norton could never detect(making my PC slow). it is very heavy software and makes your computer slow. and does not detect all the viruses. while MSE did quite a good job. so I think spending money on buying antivirus is waste if there is better application available for free.