Very exhaustive is the definition provided by the founder of BrightPlanet, Mike Bergman, that compared searching on the Internet today to dragging a net across the surface of the ocean: a great deal may be caught in the net, but there is a wealth of information that is deep and therefore missed.
Ordinary search engines to find content on the web using software called “crawlers”. This technique is ineffective for finding the hidden resources of the Web that could be classified into the following
Dynamic content : dynamic pages which are returned in response to a submitted query or accessed only through a form, especially if open-domain input elements (such as text fields) are used; such fields are hard to navigate without domain knowledge.
Unlinked content : pages which are not linked to by other pages, which may prevent Web crawling programs from accessing the content. This content is referred to as pages without backlinks (or inlinks).
Private Web : sites that require registration and login (password-protected resources).
Limited access content: sites that limit access to their pages in a technical way (e.g., using the Robots Exclusion Standard, CAPTCHAs, or no-cache Pragma HTTP headers which prohibit search engines from browsing them and creating cached copies).
Non-HTML/text content: textual content encoded in multimedia (image or video) files or specific file formats not handled by search engines.
A parallel web that has a much wider number of information represents an invaluable resource for private companies, governments, and especially cybercrime. In the imagination of many persons, the DeepWeb term is associated with the concept of anonymity that goes with criminal intents the cannot be pursued because submerged in an inaccessible world.
BitCoin system for payments allowing the purchase of any kind of products preserving the anonymity of the transaction, encouraging the development of trade in respect to any kind of illegal activities. We are facing with a with an autonomous system that advantage the exercise of criminal activities while ensuring the anonymity of transactions and the inability to track down the criminals.