Analysing a data breach – CheetahMail

I often find myself having to analyze volumes of email, looking for common factors, source addresses, URLs and so on as part of some “forensics” work, analyzing leaked emails or received spam for use as evidence in a case.
For large volumes of mail where I might want to dig down in a lot of detail or generate graphical or statistical reports I tend to use Abacus to slurp in and analyze all the emails, store them in a SQL database in an easy to handle format and then do the ad-hoc work from a SQL commandline. For smaller work, though, you can get a long way with unix commandline tools and some basic perl scripting.
This morning I received Ukrainian bride spam to a tagged address that I’d only given to one vendor, RedEnvelope, so that address has leaked to criminal spammers from somewhere. Looking at a couple of RedEnvelope’s emails I see they’re sending from a number of sources, so I decided to dig a little deeper.
I started by searching for all emails to that tagged address in my mail client, then copied all the matching emails to a newly created folder. Then I took a copy of that folder and split it into one file per email using a shell one-liner:

formail -ds sh -c 'cat >msg.$FILENO' 

I'm interested in the IP address they were sent from, so I write a tiny perl script, getips.pl, that'll look for the first Received line, and print out the IP address:


#!/usr/bin/perl
foreach my $file (@ARGV) {
    open IF, $file or die;
    while() {
        chomp;
        last if /^$/;
        if(/^Received:.*[(d+.d+.d+.d+)]/) {
            print "$1n";
            last;
        }
    }
}

I use it, along with the standard tools "sort" and "uniq" to summarize the sending IP addresses:
./getips.pl msg.* | sort | uniq -c | sort -nr
That takes the list of IP addresses generated by the perl script, then sorts them (so identical IP addresses are adjacent to each other), then counts how many times each discrete email address is found, then sorts them most to fewest. If you want to see how it does that, play around with the command line, removing commands off the end one-by-one to see the intermediate data it produces.
The result looks like this:
  27 208.49.63.243
  20 208.49.63.242
  20 208.49.63.240
  15 208.49.63.245
  15 208.49.63.241
  11 208.49.63.244
   3 38.107.108.146
   2 38.107.108.149
   2 209.112.253.83
   1 89.230.132.139
   1 38.107.108.144
   1 209.112.253.90
   1 209.112.253.85

The IP address beginning with 89 is the Ukrainian bride spam itself. Of the remainder it's easy to see that they come from three main groups of addresses - 208.49.63.0/24, 38.107.108.0/24 and 209.112.253.0/24.
The 208 and 209 ranges are both IP space owned by RedEnvelope, so that was mail sent by them directly (both transactional and advertising mail). The 38 range is space owned by the ESP Cheetahmail. (I'll go into how I worked all that out in a future post).
What does this mean? It means that either a russian bride spammer just happened to guess the email address I'd created solely to give to RedEnvelope (incredibly unlikely in this particular case, due to how I handle tagged addresses) or they stole it from somewhere. There are four places they could plausibly have stolen it from:
  1. My mail client, by compromising my laptop
  2. My mail server, by compromising the machine or the staff who run it
  3. RedEnvelope, by compromising their servers, employees or employee machines
  4. Cheetahmail, by compromising their servers, employees or employee machines
I run my own mailserver, so I know exactly which email addresses it handles. There are many hundreds or thousands of email addresses which it handles, and to which mail has been sent legitimately (as well as countless billions of addresses that it would accept email to if you made them up, but which have never been used). If it had been compromised in any way, I would expect many of those email addresses to be sent spam as part of this spam run (it's not at all unusual for 40 or 50 of my email addresses to receive copies of any given spam). But only the RedEnvelope-specific email address received the Ukrainian bride spam.
Similarly for my laptop. It has hundreds of email addresses in it's mailboxes. If it had been compromised, I'd have expected to see this spam sent to many of those email addresses, and I don't. If someone had stolen multiple email addresses of mine, I'd expect them to be sending spam to all of them, unless they were doing something clever and deceptive like spear-phishing - and Ukrainian bride spam isn't clever, subtle or targeted.
That leaves just RedEnvelope or CheetahMail as likely sources of the stolen address. Conveniently, Laura also has an account with RedEnvelope, and also uses a tagged address with them. She's seen no spam at all to her RedEnvelope-specific address. Doing the same analysis with the legitimate RedEnvelope mail she's received to that address I get this:
   2 209.112.253.90
   2 209.112.253.85
   2 208.49.63.242
   2 208.49.63.241
   1 209.112.253.83
   1 208.49.63.245

There are only three significant differences between Laura's account and mine. Mine was created in June 2010, while hers was created in December. Mine has been emailed via CheetahMail, hers hasn't. And mine received russian bride spam, hers didn't.
One possibility is that RedEnvelope were compromised prior to December, so only my address was taken. But if that were the case I'd have expected to see that address misused before today. It's possible, but not the most likely explanation.
More likely is that CheetahMail were compromised some time in the past few days, and the email address was stolen from there.
This isn't conclusive proof by any means, but if I were RedEnvelope or CheetahMail I'd be looking very closely at other reports of stolen addresses, to see if there are patterns of theft from RedEnvelope lists sent across multiple ESPs or compromises of data from multiple CheetahMail customers.
 

Related Posts

Yes, we have no IP addresses, we have no addresses today

We’ve just about run out of the Internet equivalent of a natural resource – IP addresses.

Read More

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…

Read More

What is Two Factor Authentication?

Two factor authentication, or the snappy acronym 2FA, is something that you’re going to be hearing a lot about over the next year or so, both for use by ESP employees (in an attempt to reduce the risks of data theft) and by ESP customers (attempting to reduce the chance of an account being misused to send spam). What is Authentication?
In computer security terms authentication is proving who you are – when you enter a username and a password to access your email account you’re authenticating yourself to the system using a password that only you know.
Authentication (“who you are”) is the most visible part of computer access control, but it’s usually combined with two other A’s – authorization (“what you are allowed to do”) and accounting (“who did what”) to form an access control system.
And what are the two factors?
Two factor authentication means using two independent sources of evidence to demonstrate who you are. The idea behind it is that it means an attacker need to steal two quite different bits of information, with different weaknesses and attack vectors, in order to gain access. This makes the attack scenario much more complex and difficult for an attacker to carry out.
It’s important that the different factors are independent – requiring two passwords doesn’t count as 2FA, as an attack that can get the first password can just as easily get the second password. Generally 2FA requires the user to demonstrate their identity via two out of three broad ways:

Read More