“We are what we pretend to be, so we must be careful what we pretend to be.”
|--MOTHER NIGHT, KURT VONNEGUT, JR.|
A covert channel is a secret communication pathway. Covert means hidden, so the communication must be concealed. The term originates from the design of highly secure, compartmentalized computer systems—the ones found in military installations that handle classified information.
These systems are supposed to keep one process from communicating with another process. As it turns out, that is very hard to do. No matter how minor, any detectable signal that can be influenced by two parties may become a conduit of communication between them.
A covert channel doesn’t have to be fancy or meet academic standards of stealthiness; ...