Beware of Spy Ware

We have been without our computer this week because of an infection of viruses. We pay for Norton to protect us and it has done well all this time. But the other morning I walk into the computer room to see the screen filled with filthy, vulgar pictures. Also about 5 warning windows were layered over top of the pictures. The warnings were telling us to buy their spy ware to eliminate the problems we now had. The spy ware had turned off our Norton protection, the one we pay for. There should be a law against it. Hubby had to go through all kinds of maneuvers to fix the computer. It is fixed, but not working as well as it had before. We will probably find more problems have not been caught. Seems we got the infestation from opening an email, or from any site. The disabling cookie lies dormant for a while so you cannot trace its source. Why can't it all work normally and safely?