Domain intentionally targeted by mail spammers
Saturday, December 10th, 2005I got an e-mail, that I thought was interesting enough to use here, with my reply. Munged, of course:
I need some help tracking down a spammer, and I found your site, and I was wondering if I could hire you to help me solve this problem.
I’m being attacked intentionally (for reasons that are not clear) by a spammer who is using some of my domains as their forged return address, causing me to be overwhelmed by bounces.
I know they are targeting me specifically, because I just added SPF to the main domain DNS records they were hitting, so they just switched to one of my other domains.Due to the nature of their spam (random email addresses) and how I processed email on my site (allowing wildcard addresses) it has been very difficult to filter out the bounces.
Because they are using random email addresses and because I was already using a large collection of email addresses at my domains, it has become very difficult to filter out the bounces. Furthermore, the bandwidth is choking my little server.
Could I hire you to help me figure out who the actual human being is behind this spam? I have endless bounces to look at, and I’m getting pretty desperate.
Thanks for your time.
My reply (and remember I had his headers to look at, so I had more information than what was in his e-mail):
Hi xxxx,
You said you’re being targetted intentionally, but that the reasons are not clear.
Well, that tells me it’s not intentional.
Spammers would switch FROM domains with SPF for good reason. It’s got nothing to do with you, and everything to do with SOP (Standard Operating Procedure).
Check for IP addresses on the bounces that include the original mails. Chances are extremely good that they come from all over the place.
They would rather pick domains with catch all e-mail, and without SPF, all things being equal.
If Exim doesn’t allow you to switch off catch all, I’d advise you to do set up another server instead. Postfix runs fine on Debian, and allows you to bounce mail to non-existing addresses in the SMTP handshake. Which means no more bounces, but quite a bit of handshake activity.
You can add another server as an SMTP gateway, and shunt the mail to your primary POP3 server (which can be your existing Exim server). Just change the MX records to point to the new server.
If you set it up like that, chances are extremely good they’ll stop targetting your domains.
Because this isn’t about you, it’s about maximizing the chances their spam will reach the intended targets.
If you’re not satisfied I’ve hit the nail on the head, forward some samples of spam. Including the bodies and subject lines.
Finding out exactly who’s behind the spam can be done in two ways:
1) Backwalk from an exploited machine to the IRC channel used to feed info to the zombie, then figure out who the hacker is (and yes, it’s usually a hacker hired by a spammer). This can be done from a spam, as long as you’ve got the clout to make the ISPs or companies harboring the zombies listen. But you need resources and clout to really pull it off. Even so, the incentive to keep beating the odds are enormous, because of the payoff for some types of spam.
2) Or track the payoff. Who hired the spammer or benefits from the spam.But like I said, I think I’ve cracked your case. It’s really no different from anyone else with catch all e-mail, lacking SPF or anything else that makes the domain less palatable to spammers.