All anti-software systems have a free service for just browsing and so on. You pay though even with AVG for maximum protection for anti-intrusion etc. They're all comparative, Norton might slow your computer down sightly, but all of them very effective in what they're supposed to do. I got around this by running in Admin mode otherwise you have to tell the software, program by program that it's safe.
To be fair to Norton, this is rare for it to raise the alarm so I suspect it's all part of Notorious Games evil world domination plot to make us give up our real life and become completely addicted to their game.
Although I think it's already happened with me