WhatsApp is a popular cross platform messaging app that allows users the share text, picture and video messages to either individuals or groups of friends over their internet connection.
Many of their 700 Million active users will be using the official WhatsApp app, however some may be using an unofficial app e.g. WhatsApp Plus, to access additional functionality or a different interface. However the use of an unofficial app to access the WhatsApp service is against the WhatsApp Terms of Service, and users of WhatsApp Plus are finding that they are being banned from the service for 24 hours without prior warning.
WhatsApp themselves have posted an update to their FAQ pages stating that they have taken this step to protect users of the service against potential malicious third party code.
This move may prove to be unpopular with some users of the service, especially given the lack of warning, however users of the WhatsApp service did agree to the ToS of the service when they started using the service. So there seems very little option for those who have been banned other then to accept their 24 hr break from the service.