Disclosed is a hardware based secure multi-level security computing system system. The system comprises a chassis enclosing multiple separate, secure computer devices or domains, each within an electromagnetic shielding Faraday cage. The chassis structure includes internal electromagnetic shields and other features to prevent cross domain electromagnetic interference or compromising emanations. The chassis may be the size of a standard computer tower. The computer devices or domains may be configured for handling information of different classification levels. Optionally, each of the computer devices may operate on significantly less power than a standard computer. Preferably, each computer operates on no more than 50 Watts of power, more preferably on less than 35 Watts of power.