if it's windows 10 then the built in anti virus is more than enough for the vast majority
in my experience
most of the free ones are not up to where to the builtin one is
nortons crucifies more computers each year than most of the viruses it claims to protect you against
trend is fine behind a decent firewall otherwise it's money wasted
mcafee is like avg, it is a trojan in itself
as for the plethora of others like bullguard etc
harvey norman and the magazines love you all......
let the hate spew forth...

