1. A covert channel in which one process signals information to another process by modulating its own use of system resources (e.g., CPU time) in such a way that this manipulation affects the real response time observed by the second process. 2. A covert channel in which one process signals information to another by modulating its own use of system resources (e.g., CPU time) in such a way that this manipulation affects the real response time observed by the second process.