Chris,
I have used it for years and never had a problem with it.
It is more of a barrier than an infection detector. It protects browsers from unwanted stuff. As of just now when I had an update it has a list of 9,847 items that will not get through on the browsers.
This list is updated by the company regularly and all you have to do is update and enable the updates to be listed in each browser list. It just sits there watching for unwanted items trying to get through. It works in real time but does not use much resource.
Recommend it.
dave