A functional analysis testing model was designed, and used to assess the security design weakness of android device third-party applications software. The model analyses and identify the design weakness of the captured packet strings of the chosen apps sniffed between system and networked devices. The findings provide evidence that most third-party apps are vulnerable. In most case the traffic packet strings travel over the network unencrypted. This has been proven by test analysis on mobile network applications such as WhatsApp, Games and Gumtree website. They are characterized by gathering user's information such as advert cookie, user address, location, stored images, and request URL links.