This paper describes strategies to secure military ground vehicles by using digital fingerprinting, detection algorithms, and bus segmentation to identify and remove anomalous messages from the Controller Area Network (CAN) bus. Modern automotive buses were designed for reliability rather than security. This lack of security means that any node on the bus can transmit a message to any other node, and the receiver cannot verify the sender or that the message is unaltered. The intrusion defense system (IDS) protects the bus by actively monitoring traffic on all connected busses and removing messages identified as anomalies. Digital fingerprinting combined with various detection algorithms identifies these anomalies while bus segmentation simultaneously defends the CAN bus by removing anomalous messages.