Instant messaging technology is the primary mechanism for information sharing and has been the force of success of all social networking sites. Taking this clue, government and military organizations have also started using messaging for quick and fast actions. Defense messaging system takes a message and forwards it to the intending recipients or parties based on the message criteria for immediate action. This system should provide security assurance and should be manageable by central administrative authority instead of relying on the individual users. The primary goal of this research is to develop a multilevel access control for Defense messaging system using Elliptic curve cryptography. The system developed is secure, multi site and allows for global communication using the inherent properties of Elliptic Curve cryptography. Elliptic Curve cryptography provides a greater security with less bit size and it is fast when compared to other schemes. The implementation suggests that it is a secure system which occupies fewer bits and can be used for low power devices.