virus

You don't need any 3rd party antivirus app to keep your Mac malware-free. Macs are not immune to malware, but no true viruses exist in the wild that can run on Mac OS X, and there never have been any since it was released 10 years ago. You cannot infect your Mac simply by visiting a website, unzipping a file, opening an email attachment or joining a network. The only malware in the wild that can affect Mac OS X is a handful of trojans, which cannot infect your Mac unless you actively install them, and they can be easily avoided with some basic education, common sense and care in what software you install. Also, Mac OS X Snow Leopard and Lion have anti-malware protection built in, further reducing the need for 3rd party antivirus apps.

Mac Virus/Malware FAQ​

Stay away from "maintenance" apps like MacKeeper, as they can actually reduce performance.

 

As I said in my first post, you can't infect your Mac simply by opening an email attachment. You have to actively install a trojan, which usually involves entering your admin password during the installation process.

Your email account was likely hacked, which has nothing to do with your computer or malware. If you use a secure password, there is less chance of your email account being compromised.