Odd external links from non-existent subdomains in WMT

[webdude]

On one of my sites that has a forum, I noticed as of yesterday that I was getting all sorts of odd looking URLs listed in the External Links. All of these URLs are going to specific posts (topics) in the forum. None of the subdomains exist yet a handful of the root domain seem to come up. The URLs have some keywords in them, usually in the subdomain. They look like the following

www.mytopic.cop74.example.com/related-topic
www.related-topic.dun64.example.net/related-topic-forum.php
www.another-related-topic.obe46.example.org/another-related-topic-forum.php
www.mainkeyword.rya60.example.org/looking-for-topic/
www.mainkeyword.uns28.example.nu/other-topic-forum.php

Etc. Etc. Etc.

Yesterday I found about 6 to 8 of these links going to about 20 different threads. Today, I am getting 6 to 8 of these going to several hundred threads. Tomorrow? Who knows? I can't find these using link: in Yahoo nor can I find them in Analytics, just in WMT for External Links.

Any ideas on what is going on?

[g1smd]

What happens when you try to access any of those URLs?

What HTTP response code do you get back?

Is your server allowing wildcard subdomains? If it is, you need to stop that happening.

[webdude]

First off, I handle my own DNS and our servers do not accept any wildcards. All the URLs are coming up as 404 errors. However, 90% all the root domains get the following (I removed the actual name of the company and urls)...

example.net is a domain owned by This Specific Company, Inc., but there is no content at this domain. You should be automatically redirected there in 10 seconds.

If you need to report abuse of a subdomain of example.net, this is probably owned by a customer of ours, and should be reported to our abuse department. Please send e-mail to [e-mail] with the full details of the abuse you are reporting, and we will investigate it as soon as possible.

If you are seeing this page when attempting to update a companyDNS hostname, you need to change your configuration to update using members.companydns.org instead of example.net.

Interesting... I guess I am being targetted somehow. What I don't get is why?

[vincevincevince]

All the URLs are coming up as 404 errors

I may be wrong; but that indicates to me that you are allowing wildcards. The subdomains should not be resolving to an IP address at all.

Have any of these subdomains shown up in google search results? More importantly; have you checked that the header really is a pure 404?

[phranque]

at your dns you should take all wildcard subdomains and address them to your primary domain, so that if someone accidently types in wwww.example.com you still get the traffic.
once you receive this request, you should have implemented proper domain name canonicalization such that the incorrect subdomain request returns a 301 Moved Permanently response that redirects the user agent to make the request to the correct domain, presumably www.example.com in this case.

as mentioned above you should make sure your "404 page" actually returns a 404 HTTP Response code, not a 200 OK.
also a request for a nonexistent resource should properly return a 404 response, not a 301 or 302 redirect to a 404 page.