WhatsApp Messenger is a cross-platform mobile messaging app which allows you to exchange messages without having to pay for SMS. WhatsApp Messenger is available for iPhone, BlackBerry, Android, Windows Phone and Nokia and yes, those phones can all message each other! Because WhatsApp Messenger uses the same internet data plan that you use for email and web browsing, there is no cost to message and stay in touch with your friends. WhatsApp Voice and Video calls use STUN (UDP/3478). (Note: Blocking PROTOCOLS/STUN Application will block WhatsApp Voice and Video Calls, and affect other VoIP apps as well.)

This SonicWALL signature identifies legitimate WhatsApp Messenger network traffic.