DNS redirection is the controversial practice of serving a Web page to a user that is different from either the one requested or one that might reasonably be expected, such as an error page. Typically, an ISP serves an ad-based page, rather than a 404 error message, when the user mistypes a URL.
In July 2009, Comcast announced it would test DNS redirection, under the name “Domain Name Helper Service,” in Arizona, Colorado, New Mexico, Oregon, Texas, Utah, and Washington. Other ISPs that have implemented DNS redirection over the last few years include Verizon, Cox, Earthlink and Charter. The practice is generally not popular among consumers.
ISPs also use DNS redirection to prevent customers from accessing malicious websites or websites with illegal content.
DNS redirection differs from DNS poisoning, in which an attacker gains access to a server’s DNS table and substitutes a rogue address for a valid one.
Learn More About IT:
> David Chartier discusses this issue for ars technica : ‘404 might be found: the curious case of DNS redirects.’
> See Comcast’s draft document describing DNS redirection.
> Gartner’s John Pescatore posted about ‘Security Issues of Top Level Domain DNS Redirection.‘
> MacRonin posted about DNS redirection as a violation of Net neutrality.
> Here’s Comcast’s explanation of Domain Name Helper Service.