The ubiquitous computing environment has been realized with the proliferation of wireless communication technologies, which has improved our lives in many ways. A mobile ecosystem is a representative example. We are using various services with a smartphone based on the well-organized wireless network. However, the development of the smartphone environment has brought some issues about security problems like information leakage and overcharging. Especially Android is becoming a prime target because of its high market share and characteristics of the platform. Most of attacks have been conducted through malicious applications. Recently, a large number of malicious applications have been found which performs an attack to replace existing banking applications on the system with modified ones to steal financial information without user's knowledge. Thus, we propose a method as a countermeasure for it by making a minimum change to the Android platform to provide a user with enough information to notice the application replacement attack. We expect that it will effectively reduce the damages caused by the attack.