WhatsApp has introduced two-step verification feature for its Android, iOS, and Windows Phone users. The feature was initially available only to beta users, but now is officially available to everyone.
The feature is optional, and it allows you to create a six-digit passcode which you will have to enter when your phone number is being verified on the app.
To enable two-step verification, open WhatsApp > Settings > Account > Two-step verification > Enable.
Upon enabling this feature, you can also optionally enter your email address. This email address will allow WhatsApp to send you a link via email to disable two-step verification in case you ever forget your six-digit passcode, and also to help safeguard your account.
However, be careful to enter the correct email cause WhatsApp doesn't verify your email address.
To help you remember your passcode, WhatsApp will periodically ask you to enter your passcode. There is no option to disable this without disabling the two-step verification feature.