A data bridge controls packet transfers between network fabrics forming a closed network, such as a vehicular network and a home network. The data bridge includes two or more sets of modules, each of which communicates with a different network fabric. When a packet is to be delivered between network fabrics, a first set of modules, which is used to communicate with a first network fabric, decides whether to accept the packet or discard it. If the packet is accepted, it is delivered to a second set of modules, which is used for communicating with a second network fabric. The second set of modules makes a second, independent decision about whether the packet will be sent to the second network fabric. Each set of modules can base its decision on packet content type, and may discard any packet not to be delivered to the other network.