One of the viruses that I had to do battle with when I was setting up my new laptop, was the Snap.do aka Shopping Helper.  This virus attaches itself to all of your browsers and hijacks them so that when you use your browsers, Snap.do takes you to their own web site to sell you their software products,

I have no idea where Snap.do came from or how it got past my virus protection. All I know is that it took me over 4 hours to cleanse all of my browsers and get rid of it.