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Using qpsmtpd and Amazon EC2 to provide SMTP-DDoS protection

Like a few other anti-spammers, I found myself under a hitherto-unprecedented level of spam blowback this weekend. Disappointingly, there are still thousands of SMTP servers configured to send bounce messages in response to spam.

Even with the anti-bounce ruleset for SpamAssassin, the volume was so great that our creaky old server had a lot of difficulty keeping up — once the messages got to SpamAssassin, the load issues had already been created. Also, Postfix’s anti-spam features really weren’t designed to deal with blowback.

While attempting to take some shortcuts in the setup on our server to deal with this, a great idea occurred to me — why not come up with an app that uses Amazon EC2 to flexibly provision enough server power and bandwidth to pre-filter the SMTP traffic for an MX under attack?

I’m basically thinking of qpsmtpd, with SpamAssassin and/or other antispam blobs active, running in an Amazon EC2 server image. Multiple images can be brought up, and added to the attacked domain’s MX record at an equal priority, to take load off the main (overloaded) MX.

Now to cogitate a little — details to follow…