i recently found a malware that changes bitcoin addresses when copied to the hackers address so just watch out and check to make sure that the bitcoin address you copy comes out the same when you paste it 
There are a lot malware out there come from related bitcoin service. I personally always check and scanned the site first when i want to visit, especially with a site which strange or fishy for me. This some tips for make your PC secure and avoid any virus/malware: https://bitcointalk.org/index.php?topic=203876.0