To protect your information, AT&T suggests that you password protect your device as soon as you get it, and the carrier suggests that you change your voicemail and online passwords frequently. Downloading device protection and security apps can help save your phone from getting ripped off. AT&T suggests that you backup.
The FCC is teaming up with the nation's top carriers to develop a database of stolen devices. In about six months, if your phone is lost or stolen, you will be able to call your carrier to have it locked down completely. The aforementioned database should be completed in 18 months and will be based on each phone's unique International Mobile Equipment Identities (IMEI) number.
If you don't mind us throwing in our 2 cents, to lower the chance of getting robbed of your mobile device, you should always be aware of your surroundings and don't wave around your phone or tablet if it is not being used. Police officials in New York City have compared walking around the subway with an iPhone or iPad to be the equivalent of flashing a lot of money.
source: AT&T via PCMag
AT&T's website gives you tips on keeping your smartphone information safe