DNS Inventor Warns of Next Big Threat

DNS Inventor Warns of Next Big Threat
DNS Inventor Warns of Next Big Threat 

By Kelly Jackson Higgins
Senior Editor
Dark Reading
February 11, 2008

The industry is just one multi-million-dollar corporate data breach away 
from waking up to the serious and often-silent threat of corrupted DNS 
resolution servers, says DNS inventor Paul Mockapetris.

Mockapetris -- who is also chief scientist and chairman of the board for 
network naming and address vendor Nominum -- says the recent research on 
corrupted DNS resolution servers by researchers at Georgia Tech and 
Google demonstrates yet another way the bad guys are attacking DNS to 
infect users. (See Hacking a New DNS Attack [1].)

Researchers David Dagon, Chris Lee, and Wenke Lee of Georgia Tech, and 
Google's Niels Provos, dubbed the new threat "DNS resolution path 
corruption, where malicious DNS servers provide false information in 
order to send users to malicious sites. The researchers officially 
presented their findings today at the Network and Distributed System 
Security Symposium (NDSS) in San Diego [2].

In their study of DNS resolution, they found around 17 million 
open-recursive DNS servers on the Net, and discovered that about .4 
percent, or 68,000 of them, are performing malicious operations by 
answering DNS queries with false information that sends them to 
malicious sites. About 2 percent are returning suspicious results, they 

This report demonstrates that people are getting lured out to dark 
alleyways of the Internet. The actual damage isnt documented here, but 
it will be somewhere when someone loses the first $10 million to $100 
million to this type of attack, Mockapetris says.

This growing method of attack forces users to rely on rogue DNS servers, 
which results in what the researchers call a second secret authority on 
the Internet. They found dozens of viruses that infect DNS resolution 
paths, and that hundreds of URLs each week do drive-by alterations of 
host DNS settings.

There are obviously legitimate reasons for redirecting or editing a DNS 
entry/registry, such as with organizations like OpenDNS that block 
unwanted sites and correct fat-fingering mistakes from sending a user to 
a typo-squatter's site. But users need to be aware that the bad guys 
have also figured out how to abuse DNS this way, Mockapetris says.

So a user working off a public WiFi port, for example, is at the mercy 
of the DNS servers it uses, which "could easily be malicious," he says.

The Georgia Tech and Google researchers focused on malicious alteration 
of DNS answers in their study. Companies are rewriting DNS answers, 
ideally to improve the user experience, but also to expose the users to 
ads, says Georgia Techs Dagon. There are also some laudable security 
improvements that come from rewriting answers. For example, OpenDNS can 
protect users from malicious sites. But DNS vendors aren't the only ones 
commercializing the alteration of DNS traffic. Malware authors also use 
this technique to exploit victims.

Nominums Mockapetris says combating this threat may require revisiting 
the DNS food chain -- meaning data from the user who owns the domain, to 
the user who wants to access it, and who gets to modify it, he says. The 
fewer places [it gets modified], the better.

The researchers focused on incorrect and malicious answers provided by 
DNS machines, Dagon says. The... alteration of DNS answers deserves 
further study. In service of that goal, we will make data from the 
ongoing study available to the research and DNS communities, he says.


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