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, the programmable logic device being separate from a processor of a single board computer operably coupled to the programmable logic device such that processing associated with the filter engine is offloaded from the processor of the single board computer to the programmable logic device; 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, the message rule being located in a rule file comprising a plurality of message rules, the rule file being dynamically determined based on one or more characteristics of the message; 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.