I have been using this for over five years and never had a problem or a virus - it's an excellent product. I'm always surprised to see all the negative comments about Norton generally, as I have not found this slow, intrusive or anything else. It does things quietly in the background - keeps you safe and up to date and has an excellent tuning section which scans the registry if you want to do this and it is surprising how much rubbish it cleans out when you have installed or uninstalled software.
Before using this I had lots of problems on my computer - I have been problem free for five years, and have even used this on a tiny 8gb netbook with 900mhz celeron processor and it is absolutely fine.
So if your mouse suddenly starts shooting around for some reason (a common issue) try running the registry scan and the problem will be solved - it will be some piece of junk that got left behind after installing or uninstalling software.