If you have Norton/Symantec or McAffee products get rid of them...they are very poor at stopping malware.
I often hear people say that about Norton. Have have been using Norton for years, currently Norton 360 3.0 with no problems. We even browse the internet with Explorer. However, we make sure to keep everything updated. We do have a faily hot machine with plenty of memory (as I've heard past versions of Norton can be a hawg).
I run malwarebytes and spyboth s&d every couple of weeks with no problems found. Spybot usually picks up on a few extra cookies.
We use an ongoing online backup as well as an external hard drive that I do a backup on about every two weeks.
Norton has worked for us and its automatic options seemed to have done the trick because often I am gone for one to two weeks at a time for work.
This computer is used mainly by mother-in-law, wife and 11 year old daughter and she plays kid games online.