Account security is fairly basic. First, change your Bnet logon email to something you use for only that. Grab a free gmail account or whatever, but dont use that account for anything. Make it as secure as you can with letters and numbers. Dont use the same email acc/pw that you use elsewhere on the tubes like facebook, or logons to you're favorite wow website.

Account Password should be MS Complex compatible at a minimum. Use upper and lower case letters, a number and a special character and at least 8 characters long.

Use a dedicated box to browse the web. Dont have one? then create a virtual machine and do your web browsing in there. Yea its extreme, but you gave your account information to the hacker either directly by signing up with the same info or downloading/clicking something that did.