The Cone of Silence is one of many joke devices from the Get Smart American comedy television series.

In the series, whenever Agent 86 wanted to speak to his boss with no eaves-droppers, a "Cone of Silence" would be lowered over their heads: this device took the shape of two interconnected bowls, or literal cones, with many humourous variations and which never works as intended.

The term has been adopted in pop-culture for any system that prevents eavesdropping, usually by creating a private or encrypted link between the clients. VPNs (Virtual Private Networks) are a good example, as is any form of encrypted or hidden instant messaging.

The term "Cone of Silence" is also used when people are overtly zealous in trying to keep a secret: here the term usually refers to the fact that the 'outsider' can see something is there, but he is unable to find out exactly what.