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How to disable a domain

Sometimes you might want to make it clear that a domain isn’t valid for email.
Perhaps it’s a domain or subdomain that’s just used for infrastructure, perhaps it’s a brand-specific domain you’re only using for a website. Or perhaps you’re a target for phishing and you’ve acquired some lookalike domains, either pre-emptively or after enforcement action against a phisher, and you want to make clear that the domain isn’t legitimate for email.
There are several things to check before disabling email.
1. Are you receiving email at the domain? Is anyone else?
Check the MX records for the domain, using “host -t mx example.com” from a unix commandline, or using an online DNS tool such as xnnd.com.
If they’re pointing at a mailserver you control, check to see where that mail goes. Has anything been sent there recently?
If they’re pointing at a mailserver that isn’t yours, try and find out why.
If there are no MX records, but there is an A record for the domain then mail will be delivered there instead. Check whether that machine receives email for the domain and, if so, what it does with it.
Try sending mail to postmaster@ the domain, for instance postmaster@example.com. If you don’t get a bounce within a few minutes then that mail may be being delivered somewhere.
2. Are you sending email from the domain? Is anyone else?
You’re more likely to know whether you’re sending mail using the domain, but there’s a special case that many people forget. If there’s a server that has as it’s hostname the domain you’re trying to shut down then any system software running no that server – monitoring software, security alerts, output from cron and so on – is probably using that hostname to send mail. If so, fix that before you go any further.
3. Will you need mail sent to that domain for retrieving passwords?
If there are any services that might have been set up using an email address at the domain then you might need a working email address there to retrieve lost passwords. Having to set email back up for the domain in the future to recover a password is time consuming and annoying.
The domain registration for the domain itself is a common case, but if there’s any dns or web hosting being used for the domain, check the contact information being used there.
4. How will people contact you about the domain?
Even if you’re not using the domain for email it’s quite possible that someone may need to contact you about the domain, and odds are good they’ll want to use email. Make sure that the domain registration includes valid contact information that identifies you as the owner and allows people to contact you easily.
If you’re hosting web content using the domain, make sure there’s some way to contact you listed there. If you’re not, consider putting a minimal webpage there explaining the ownership, with a link to your main corporate website.
5. Disabling email
The easiest way to disable email for a domain is to add three DNS records for the domain. In bind format, they look like:

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Authentication and phishing

Yahoo announced today that they are releasing the Yahoo! Mail Anti-Phishing Platform (YMAP) that will help protect their users from phishing. They have a similar project in place for eBay and PayPal mail, but this will extend to a broader range of companies.

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Targeted attacks via email – phishing for WoW gold

You’re going to be seeing a lot of discussion about email addresses stolen from ESPs in the next few days, if you haven’t already. There are a lot of interesting things to discuss about that from an email perspective – from “Why two factor authentication isn’t a magic bullet.” to “And this is why corporate spam folders can be a major security risk.”
We could have fodder for blog content for weeks!
Right now I’m just going to look at one of the reasons why it’s worth stealing a list of email addresses from an ESP or a list owner, rather than just gathering them from other sources. That is, why the ESPs and list owners are high value targets beyond just “that’s where the email addresses are“.
If you steal a list of addresses from a list owner, or a bunch of lists from an ESP, you have one very useful extra piece of information about the recipients beyond the usual name-and-email-address. You know a company that the recipient is already expecting to receive email from.
That means that you know someone you can pretend to be in order to get a recipient to open and respond to a malicious email you send them – which will make an attempt to phish someones credentials or compromise their computer via email much more likely to be effective.
A good example of targeted phishing for credentials is the online game World of Warcraft. There’s a huge criminal underground that makes real world money by selling game money to players. The main thing the gold sellers need to have to be able to acquire game money, advertise their services to players and to give game money to players in return for dollars is an endless series of World of Warcraft accounts. Blizzard, the World of Warcraft owner, work reasonably hard to squash those accounts and make it slightly tricky for the gold sellers to sign up for them, so stealing account credentials from existing users is a great way to get them. And you can also strip those accounts bare of in-game possessions and gold in the process.
Some of the phishing is done in the game itself, where you know that everyone has an account you can steal if you can just get them to visit your website and compromise their machine…

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