To secretly hack WhatsApp messages, isn't easy. However, WhatsApp might be a little-known messaging app in the US. But in many parts of the globe. It's an essential part of everyday life. The Facebook-owned app is easily one of the most popular messaging services in the world. However, to understand WhatsApp's popularity, you need to understand it was one of the first mobile apps to offer free, internet-based messaging. Instead of sending texts using cellular-data networks, where fees may apply, WhatsApp primarily relies on a Wi-Fi connection to send and receive messages and calls for free.