Protecting Your DNS

There have been several recent Denial of Service attacks reported on banks, hosting providers and federal agencies around the world.  As always with these types of attacks, one of the victims is the DNS server. Attacking DNS is effective, once the DNS server is taken down by the hacker, customers can’t reach any of the victim’s servers including mail servers, web servers, etc.

Besides the effectiveness there are also other reasons why the DNS server is the bully victim of the Internet. One of the more technical reasons is that DNS service is UDP based and not TCP based like most other services. Many simple types of attacks can be performed towards UDP based system.  Additionally, UDP is also much easier to forge than TCP so the hacker does not have to reveal his IP-address in the attack. All of this makes the DNS a juicy target.

The traditional way of protecting DNS and other servers is via stateful firewalls. However, this protection mechanism does not work well for UDP based attacks. In fact, most firewalls actually contribute to the problem rather than helping since they are not designed to cope with large floods of small packets. You can verify that this is the case by reading the fine print in the specifications of your firewall. It is probably rated at an impressive number of gigabytes per second but if you look at the number of packets, it is not that high. And even if you have a firewall capable of millions of packets per second it will not do you much good as it is not doing much inspection of the DNS traffic. Traditional firewalls are not smart enough and do not look far enough into the packet to really be able to determine if the packet is legit or not.

What is really needed for adequate protection is a specialized DNS firewall that sits outside of the firewall. This device can either be configured with the DNS data so that it can respond directly or simply forward the scrubbed traffic to “softer” DNS servers behind it.

Secure64’s products can be used in such a setup. Our products defend against Denial of Service attacks and other types of attacks directed towards the DNS servers while we are still able to respond to legitimate traffic. For more information on our products please visit us at our web site.