The deep web (also referred to as the invisible web, hidden web, or deepnet) is a large section of content on the World Wide Web that isn't catalogued by standard search engines. Most of the deep web contains harmless information, but it can also foster serious criminal activity. The deep web is quite large; several times the size of the surface web.
The phrase "deep web" was coined by Mike Bergman, founder of data collection service Bright Planet, in August 2001. In his white paper "The Deep Web: Surfacing Hidden Value," Bergman compares searching the Internet to casting a fishing net onto the surface of the ocean. A lot may be caught in the net, but a vast amount of information is too deep for the net to catch. Web pages can "sink" into the deep Web if there are no other pages linking to them.
- Read The Deep Web: Surfacing Hidden Value, hosted at the University of Michigan.