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I thought I was being DDOSed. Turns out I'm not that important...

The real pain came in dealing with UK cops

Beginner's guide to SSL certificates

Opinion Stuck at home with man-flu (well, a grotty man-cold) I noticed a couple of days ago that I could not send outgoing mail because my mail server was refusing connections. Even from me.

On my small (SheevaPlug) system I set it up so that the machine never need swap or page and stays responsive, and it just rejects extra work if it is too busy.

But it's a sure sign that I'm getting SPAMmed, and a quick bit of ps love shows lots of stuff like this.

Note the "rejecting connections" in the last line: that's because the system has allocated all the resources (memory, TCP state, etc) that it is prepared to allocate – and not one of those open connections is at all legitimate, by the way.

Most but not all of the incoming connections are from China and Taiwan; some, however is from the UK and places closer to home.

Look at the MADEUPNAME@my.domain line: all the connections that I've examined seem to be attempts to deliver ~32kByte messages from the mailer daemon to random (non-existent) user IDs at one of my (vanity) domains. Which implies that it's either a deliberate attempt to DDoS my mail system since nothing can get through, or it may be backscatter from a "Joe Job*" sending faked emails with forged "from" addresses at my domain.

I use SPF for the domain in question, making it clear that the only legitimate source of mails from the domain in question would be my server, so backscatter could only come through relatively poorly configured mail servers that wrongly accepted forged mail in the first place, and other indicators indeed suggest that the main incoming sources are badly set up.

I do all the usual validation with reverse lookups (rDNS) and Spamhaus's ZEN blacklist, so not one of these is resulting in any mail getting to my own mailboxes.

I've received no demands for money or evidence of other BadStuff(TM) being done to me under cover of this apparent DDoS, so why, I wonder?

Actually, some other clues do suggest backscatter from someone using my domain to forge emails "from", such as an unusually large DMARC report from Google today involving that affected domain.

So my mail system is just invisible collateral damage in some Far East SPAM splurge, and I get little or no email for days on end on my main mail server. No one is actually bothered about me at all!

Incidentally, I contacted the police to let them know for stats purposes, first trying the NCA, which directed me to my local plod (well, I used 101 instead), who directed me to Action Fraud "a central point of contact for information about fraud and financially motivated internet crime"), which took some details and at least seemed to understand what a DoS attack was.

I don't expect them to be able to do anything to help, and they haven't got back to me so far. I also let my ISP know out of courtesy, though the actual packet flows are quite small.

So, it's not all about me, and like the man-cold filling my brain with fog, I just have to sit this one out and hope that it clears up of its own accord before too long so I get my main inbound email working reliably again. In the interim I'm on my backup email addy using one of the big email providers, and filed this copy that route. ®

Beginner's guide to SSL certificates

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