How to Secure Your WhatsApp from Hacking?

Two-step verification is an optional but very important feature that adds more security to your account. When you have two-step verification enabled, any attempt to verify your phone number on WhatsApp must be accompanied by the six-digit passcode that you created using this feature.
Important: If you receive an email to disable two-step verification, but did not request this, do not click on the link. Someone could be attempting to verify your phone number on WhatsApp.
Note: 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.
Source:WhatsApp