Deleting domain services: What database do they query?

Where do they get lists of expiring domains from? How are the lists created?

[golles]

Just a quick question. What database do the sites that report the lists of 'deleted' or 'soon to expire' domain names query to get their information?

Thanks

[jmccormac]

By checking the zone files for .com/net/org/biz/info et cetra against each other, it is possible to build a deleted list. However you will need to sign contracts with some of the registries for access to the zone files and the cctld registries typically will not allow zone file access.

Regards...jmcc