We reported about 12’000 users and 250’000 queries per minute back in August 2007, which grew to about 100’000 to 200’000 users in November 2008. Since then, especially the “indirect” usage of dnswl.org data has grown (through rsync data).
While we are not in a position to reveal exact names since we never asked for permission, there are a couple of things we can say (unless noted otherwise, data is as of July 2009):
We have over 65’000 unique /24 networks querying our public nameservers (up from 55’000 in August 2008).
There are about 500 unique /24 networks retrieving our data via rsync (up from 350 in August 2008).
The rbldnsd-files are downloaded most often, but the Postfix-formatted files are not far behind. And five sites are downloading the Lotus-Notes-formatted files :-)
The public nameservers handle about 250 to 300 mio queries per day.
This number depends on the world-wide spam activity, and is about the same as in July/August 2008 (before the drop in spam levels as a consequence of the shutdown of McColo).
OpenDNS.com and UltraDNS.com serve their users locally cached data, thus greatly reducing the load on our public nameservers.
Monthly traffic for a DNS-only server is about 100 Gbyte.
Many big players in the managed email and email appliance markets retrieve our data through rsync.
Some fellow DNSBL admins seem to use our data for various purposes. Hi, guys :-)
A lot of educational institutes around the world (eg from Turkey, Germany, Argentina)
Many small and large ISPs query our data through the public nameservers (and we constantly chase them in order to switch to rsync transfer…).
There are only few large commercial users in the Top 500 users of the public nameservers, but there are many of the provider names one would expect to serve such customers directly.