What does the term 'covert channel' imply in cybersecurity?

• A. A channel that is always encrypted.
• B. A standard, approved communication channel.
• C. A channel used for legitimate admin tasks only.
• D. A method of communication that is not intended for the purpose it is being used.

Answer: (D)

Covert channel means a way to move information secretly through a path that wasn’t designed for data transfer or is used in a way that bypasses normal security controls. It isn’t defined by encryption, nor by being a standard or approved channel, and it isn’t limited to legitimate admin tasks. The essence is that the communication is used for purposes it wasn’t intended for, often to exfiltrate data or evade monitoring. For example, encoding information in timing patterns or in non-obvious changes to system state can convey data without using a designated secure channel.