My macbook pro downloads links on the internet that I click?

Hello, I've had my Macbook Pro for about 2 and 1/2 years now. Recently, I've been browsing the internet and sometimes when I click on a link, Safari automatically downloads the link. I also remember a suspicious file on my desktop that seemed to be a link to an internet page. I think it was titled "4 other people". I am not sure what it was so I deleted it. This occurred a couple months back. Should I be worried? Also what sorts of symptoms should I be looking for to suspect malware activity? My screen sometimes turns white and sometimes the screen display color turns converts from the regular display color to a light blue color. This occurred after an update so I'm not sure if it deals with malware.