It's not really a secret. Cable companies don't have the bandwidth to serve all channels you can get with a box to all customers all the time. They map channels to different frequencies and your cable box intelligently tunes into the assigned frequency it's given from the addressable units. What you see as channel 800 on a cable box can be different frequencies at different times of day.
Those frequencies = channels on your ATSC tuner equipped television, and the signals are often unencrypted for PPV and OnDemand customer requested viewing. You should get a certain number of channels that don't change frequency, and those are always your local stations and a handful of cable stations. If someone in your segment requests OnDemand programming you'll see their video feed on a high channel, and can even tell when they fast forward or rewind as it's merely their box sending a signal back to the server and the cable company doing the work for them.
