Whatsapp secures accounts with 2-step verification

Whatsapp completed its testing phase and now has been slowely and steadily releasing two-step verification to many of its users across the globe.

Two-step verification : It is an optional feature that adds more security to your account. If enabled, any attempt to verify your phone number on Whatsapp will be accompanied by a six-digit passcode of your own choosing.
Enable two-step verification : For enabling this feature, you need to open your whatsapp account, go to Setting > Account > Two-step verification and then click on Enable.
You will get a optional feature of adding your email address. This email address will allow whatsapp to to send you a link to disable two-step verfication in case you ever forget the six-digit passcode you set, and also to help safeguard your account.

In order to make sure you don't foret your passcode, whatsapp will keep asking you for your passcode periodically. It can be turned off without turning off two-step verification entirely.