I just got a computer upgrade at work. I have a new Mac Pro running OS 10.9.5. I no more than got my software loaded and noticed I have some sort of malware or virus when I run Firefox. From what I've read, it sounds similar to the mac defender malware. I have loaded two different free virus detectors - Sophos and another one. Their scans did find three trojans and removed them but I continue to have the same issue. Strange windows pop up in firefox telling me I should download security software. The sites look official and use official names, but I know they are not. Anyone have any suggestions?