The leader is IBM, which has received $4.9 billion from DHS, most of it for automatic data processing systems and services. (And DHS isn’t even its biggest federal customer. That would be the Department of Defense, which pays IBM more than $6 billion). Right behind is Integrated Coast Guard Systems, which makes radio navigation equipment, at just about $11.5 million less than IBM. They are followed by Computer Systems Corporation at $4.1 billion and Lockheed Martin at $3.9 billion.