Using BIND to reduce ad server content


Internet advertising has become big business, and we see the effects of it in almost every page we view. The ad content typically comes from one or more well known ad servers, and some folks have come up with some clever ways (e.g., hosts files, DNS integration, etc.) to minimize the “ad effect” in the content we view. I have been using Mike’s host file for quiet some time, but for some reason OS X (actually lookupd) doesn’t handle large hosts files real well. Since OS X would get bogged down during DNS resolution, I decided to merge all of the ad domains into DNS to centrally fix the problem for the clients I support.

This was super easy to do, and only required two steps (assuming you are already running bind). The first step is to add one “zone” statement to named.conf for each ad domain you want to nix. The following example shows the named.conf entry you would add for the ad domain adservers.com:

zone "adservers.com"
{
type master; notify no; file "master/null.zone";
};

You can get a comprehensive list of the well known ad server domains from the ad blocking website. Once you retrieve the list, you can merge the domains into the named.conf using a combination of shell utilities, or you can download the Perl script (updateads.pl) I wrote to automate this process. The Perl script grabs the latest host file from the ad blocking website, formats the data, and spits out several lines that can be appended to named.conf:

$ updateads.pl |more

zone "ad1.com" { type master; notify no; file "master/null.zone"; };
zone "ad2.com" { type master; notify no; file "master/null.zone"; };
zone "ad3.com" { type master; notify no; file "master/null.zone"; };
[ ..... ]

Once you add all of the domains to named.conf, you need to create a zone file with one wildcard A record (this record is what is used to remove the ad servers, since the wildcard record will translate all entries in a given domain to 127.0.0.1). I am currently using the following zone file (with different domain names) to implement my ad blocking solution:

; File: null.zone
; Last modified: 07-10-2005
$TTL 86400 

@ IN SOA ns.mydomain.com hostmaster.mydomain.com. (
2005071005 ; serial number YYYYMMDDNN
28800 ; refresh 8 hours
7200 ; retry 2 hours
864000 ; expire 10 days
86400 ) ; min ttl 1 day
NS ns.mydomain.com.

A 127.0.0.1
IN A 127.0.0.1

I have found that using this technique speeds up the time it takes to render a page, enhances privacy, and will also cut down on the amount of traffic consumed by your site. Tis good stuff!

This article was posted by Matty on 2006-05-27 15:01:00 -0400 EDT