Check out this neat new project at anonwhois.org: It's domain data, published in a format similar to a URI DNSBL or RHSBL (right-hand side BL). Meaning, in short, it's a DNS-based list that you can check domains against. What does it tell you? Whether or not a domain is registered anonymously; that is to say, whether or not a domain is registered behind a "privacy protect"-like service. Like many other spam fighters, I've long considered it a bad idea to hide ownership of your domain in this manner. And now, if you, like me, think it's a bad idea, you could use the ANONWHOIS data to help score or otherwise identify messages that come from such domains or use such domains in images or links.
Project creator Blaine Fleming is quick to caution that this is not a blacklist and wasn't meant to be used for outright rejection of mail. If you use it for that purpose, you're likely to encounter false positives; as certainly, a non-zero amount of non-spam mail comes from anonymized domains.
Blaine mines the DNS query data to look for domains that require querying and categorization. I think that means that there could be a scenario wherein the first time somebody queries about a given domain, there may be no data, but if you come back later, ANONWHOIS may have figured out by then that the domain ownership info is obscured and that therefore, it merits listing. I'm sure that they need to ration and space out WHOIS lookup requests; they don't want to get blocked for running thousands of WHOIS lookups in batch.
With the recent court ruling that masking domain ownership issue constitutes material falsification under CAN-SPAM, using this data to vet marketers and other mail-sending entities strikes me an exceptionally good idea. It wouldn't surprise me to find blacklists declining to remove entities from domain or IP address-based blacklists if the domains being used don't have transparent ownership information attached to them in WHOIS.
Visit the ANONWHOIS website at anonwhois.org for more information.
Update: What do spamfighters think of anonymous whois? I asked a few, and here's what they told me.
Update: Before commenting, read my follow up post here, where I answer some commonly raised questions.