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Finding customers of a web hosting provider

How would it be possible to search for web sites that are using the web presence of a certain provider?

And assuming that the web provider didn't always develop each such web site, IE, there is no banner or logo or ad text in the web sites that you could "Google" for?

It seems to me that a given a web site, it can always be "tested" as follows: get IP address given domain name; the IP address can be looked up against the database of IP address blocks (ICANN?) to determine the owner, IE, the web provider.

But how could this process be automated "backward" to find web sites hosted by a particular provider?

Thursday, July 29, 2004

I think you'd have to take a look at the hosting company's DNS server and see what sites they are the authoritative source for the listing.  Not quite sure how that's done, as I've never played with DNS.

Thursday, July 29, 2004

Sure you can do something like that. is one such example

Reverse IP:     Web server hosts 9 websites  (reverse ip tool requires free login)

6 more domains found...

And Netcraft can tell you the IP block owner, but that won't necessarily pin you down to a hosting provider, because they could be a reseller or just own a few servers in a larger datafarm.

Netblock Owner: Peer1 Internet Bandwidth

Sites with longest running systems at Peer1 Internet Bandwidth
Peer1 Internet Bandwidth Vancouver BC CA:,,

Though, this is non-conclusive, as they don't check every website, just the ones that are requested through their service.
Thursday, July 29, 2004

And if the DNS server is listed like this?

Domain servers in listed order:
Thursday, July 29, 2004

But it is possible to give the same server more than 1 IP address, and indeed you can give every site on the server it's own IP address, so that kind of lookup won't necessarily work.
Thursday, July 29, 2004

These guys might be able to help on this:

Peter Ibbotson
Friday, July 30, 2004

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