Apple recently added the ability to turn on two step authentication when using your Apple ID. It is optional of course but adds a very strong (and important) level of security to your Apple profile.
From the Apple Website:
Why should I use two-step verification with my Apple ID?
Your Apple ID is the key to many important things you do with Apple, such as purchasing from the iTunes and App Stores, keeping personal information up-to-date across your devices with iCloud, and locating, locking, or wiping your devices. Two-step verification is a feature you can use to keep your Apple ID as secure as possible.
As the name implies, two step authentication involves two things to access your account – something you know (your password) and something you have (your phone). This prevents that 12 year old genius hacker on the other side of the world from guessing your password. Even if someone looks over your shoulder and sees your password, they’ll still need the code generated on your phone to access your account. Since the code on your phone is different each time there is no way for them to break in.
Frequently asked questions and instructions how to set this up: http://support.apple.com/kb/HT5570