YOU ARE DOING IT WRONG! I been a tech 22+ years and work in a computer shop that runs 360 Total Security ever since it came out and had NO issues with it, Firefox had issues in version 52 that prevented 360 add-on from installing properly, This Add-on prevents malicious websites from infecting your PC with malicious code snippets and auto-installers(to the one asking what it does) and finally It works perfectly in free mode, we been using & giving to customers since it came out & it saved my arse & others MANY TIMES! So please use your brains & think before you write negative feedback because you are too unintelligent to figure out such a simple & diverse anti-virus..