A method and system for secured data communication where a plurality of users communicate through ports on a common communication channel. The users communicate by transmitting and receiving data packets. The data packets are transmitted with a variety of fields of information, including but not limited to a destination address, a source address and a source port ID. A security module is connected to the common communication channel and reads the data packet contents and the source port ID. The security module then checks this information to see if the data packet is eligible to be transmitted on the common communication channel and to check which ports are eligible to receive the data packet. If the data packet is not eligible to be transmitted on the common communication channel, the security module destroys the data packet. The security module also sends out a security message on a security channel indicating which ports are eligible to receive the data packet. Each port reads the security message on the security channel and either passes the data packet to the respective user or blocks the data packet if the port is not one of the eligible ports.