DNS redirection

About
DNS redirection is the practice of configuring a DNS server to return an actual IP address when queried with an unknown domain name.

A properly-configured DNS server would report that the domain name could not be resolved, but some ISPs (especially larger ones) have found it useful to redirect such requests to a server which can respond by displaying a "search page" (if the query is an http request). This search page can then be monetized, increasing the company's profits while making diagnosis of DNS problems in their customers' networks more difficult.

Companies known to practice DNS redirection include:
 * Verizon, as of 2010 -- see 8.15.7.117, 63.251.179.13
 * Earthlink, as of 2006 -- it is possible they have since discontinued this