Security: Possible to determine all subdomains?

Hi kids, hope everyone is having a grand summer. I was thinking about security lately and was wondering if any of you knew the answer to this:

Is there a way anyone to determine all the subdomains for a particular TLD?

Just wondering how paranoid I should be about someone snooping at all my subdomains.

It looks like Dreamhost has blocked access to viewing a domain's full DNS records, so the casual (or not-so-casual) searcher is unlikely to find which subdomains you're hiding.

-Scott

Leaving aside the possibility of brute-force DNS lookups, the only real way to do this would be to do a zone transfer from Dreamhost's nameservers, but I assume these transfers are restricted to allowed slave servers only.

"Secret" web sites can still become known though, if they're spidered by a search engine or appear in referral logs.

The real question is why does it matter? If you've got something sensitive on the web, password protect it, don't rely on luck to keep it secret.

Ya'll are too kind. That's what I thought, but I'm no master. And yes, thanks for emphasizing the fact that obscurity is not security, I do pwd protect sensitive stuff.

Cheers!