Deep Web

deep web, a part of the Internet that extends beyond the reach of search engines such as Google, Yahoo!, and Bing because it includes unindexed sites, fee-for-service (FFS) content, and private databases such as password-protected e-mail accounts. The term was coined in 2001 by computer scientist Michael K. Bergman, who differentiated it from the “surface web,” where openly viewable and retrievable content resides. The deep web is also known as the “invisible web” or “hidden web,” but it should not be confused with the “dark web,” where encrypted content with hidden IP addresses resides. Called “dark” because it is accessible with anonymity and only through certain networks and software such as Tor, this part of the Internet represents a small fraction of the overall Web.

The deep web represents a vast array of data and content. In fact, it is likely some 500 times larger than the surface web and may contain as much as 96 percent of online content. Much of this content is in the form of databases that are accessible only by password or subscription or for a fee.