Many marketing pros have no interest in technology, and when I bring up subjects like the deep web and the dark web, their eyes glaze over and they quickly reach for their phones. But after researching online reputation issues for my new book How to Protect (Or Destroy) Your Reputation Online, I can say with absolute certainty that marketing professionals who ignore the deep web and the dark web do so at their organization’s or their client’s peril.

We begin most of our online interactions through a search engine like Google or Bing, or we access information directly through mobile apps associated with Facebook, CNN, the Weather Channel or another organization that makes its offerings easily reachable. This part of the internet, which everyone can see and is indexed by search engines, is known as the “surface web” and sometimes called the clear web or visible web.

However, vast amounts of information and data are exchanged out of the sight of search engines. Known as the “deep web,” this includes dynamic web pages, blocked sites, unlinked sites, private sites (like those that require login credentials), non-HTML content and private networks. Some estimates suggest the amount of information on the deep web (also known as the deep net, invisible web or hidden web) is 500 times greater than the surface web.