How To Prevent Malware on Lion & Snow Leopard Macs
Use a non-admin account: Step 3
If the machine prompts about automatic log-in, turn it off. Until you have finished securing the machine, remain logged in as the administrator account. Once you do log into your new, secure non-admin user account, you'll have to set up your email and browser settings again, as well as re-sync any cloud services such as Dropbox.