Method, system and computer program product for protecting the integrity of data transferred between an input/output bus of a data processing system and an external network. A method for protecting the integrity of data transferred between an input/output bus and a network includes generating a Cyclic Redundancy Check (CRC) value on an interface between the input/output bus and an adapter for data being transferred from the input/output bus to the network, and checking a CRC value on the interface between the input/output bus and the adapter for data being transferred from the network to the input/output bus. By adding a CRC generator and a CRC checker on the interface between the input/output bus and the adapter, end-to-end data integrity protection is provided for data transferred between the input/output bus and the network.