H guys, I have a mid-2011 27" iMac that has recently started popping up with windows saying that I have malware. Now I'm not sure if these are official mac prompts or windows popping up from the site I'm looking at. I sometimes have to force quit Safari to be able to close the window. Can someone let me know how I can scan or check my iMac for malware etc? I've never installed any sort of virus protection as I was told that iMac's don't need it. Thanks for your help. Richard.