When a private information security incident occurs, the people who own the information are not acknowledged about their information leakage until those affairs appear in public media. This research aims at developing a mobile alarm system for acknowledging suspicious events to the information owners. The mobile alarm system was designed considering the limited user interface of mobile terminal and concept of "personal information leakage message tree" is deployed. The message tree contains every possible situation about personal information leakage and the leaves of the tree has several choices that the information owner can select. This message tree concept enables each information owner to manager his or her information leakage situation by just pushing a few buttons of mobile device. The contribution of this paper is in design of a comprehensive alarm message tree and development of mobile alarm system containing the message tree concept.