The growth in the number of mobile wireless data users is forecast to grow three fold in two years. This paper provides an introduction to security aspects of mobile device communication. The concepts of confidentiality, integrity, availability, and legitimate use are presented to inform the non-security specialist on issues that will impact their systems in the near future. The six fundamental threats: denial of service, unauthorized use, data integrity loss, data confidentiality, and data repudiation are covered. Counter measures important to mobile device developers to prevent against security threats are encryption, seals, and signature authentication. The final section provides an overview of several security topologies prevalent in today’s mobile systems.