1. An apparatus for hardware-based filtering in a multi-level secure cross-domain infrastructure, the apparatus comprising: a programmable logic device comprising a filter engine, the filter engine in communication with a first security module; an interface module of the filter engine configured to receive a message from the first security module, the message being sent from the first security module to a second security module, wherein the second security module comprises a different security classification than the first security module; a filter module of the filter engine configured to filter message data contained within the message according to a message rule, the message rule defining a data compliance requirement associated with the security classification of the second security module; and a routing module configured to provide the message to the second security module in response to the message data complying with the message rule.