From The Erbo Files
Thursday, February 9, 2012

I got an odd E-mail from an old friend of mine the other night; no subject line, a number of other people on the To: line, and the text body consisting of just one thing: a URL from a site with a .cz domain (the Czech Republic).  Anyone who's been on the Internet for more than a week should either have alarm bells going off in their subconscious at this point, or shouldn't be allowed out without a keeper.  Best hypothesis: her machine or E-mail account was compromised somehow and is sending this mail out as an attempt to infect others.

Actually clicking on a link you get in an E-mail like this is about as wise as wandering down Skid Row, grabbing a hypodermic needle from a random junkie you find passed out on the sidewalk, and jamming that needle into your own arm. Fortunately, I have some techniques that are the equivalent of working from behind leaded glass and fishing at it with tongs, namely, using the wget command on a Linux box to fetch the contents at that URL to a file without executing it, and then using a text editor to open the file, again without executing it.

The contents of that first file I pulled from behind that URL were roughly like this:

<script type="text/javascript" src="(another Czech URL)"></script>
<meta HTTP-EQUIV="REFRESH" content="0; url=(a URL in Russia)">

Right away, it's obvious someone's trying to play games. That <meta> tag is trying to force the browser to read from another site almost immediately. Trying to pull from the Russian site, however, got no results; the site returned no data and timed out.

But what about that JavaScript?  Pulling it revealed some other trickery:

if (top.location.href==self.location.href) {
document.writeln('(an entire HTML document, pretty much)');
document.write('<script type="text/javascript" src="(a Google Analytics JavaScript URL)"></script>');
document.write('<script type="text/javascript" src="(a URL loading a script with the same name, but from a Czech site)"></script>');

More deliberate obfuscation, and what looks like an attempt to hijack Google Analytics, perhaps to make the site seem more popular than it is. (Any function declared in the presumably-legit Google Analytics script, but then re-declared in the Czech script, would use the latter definition.) The document being written in that first document.writeln() call contains a lot of obfuscation, too. (The most obvious obfuscation was that it was written all as one line, defying easy viewing; I had to pass the script text through fold -80 to get it into a state where I could read it.) It has a lot of CSS styles, both in an embedded stylesheet and inline; many of the styles are marked as !important, meaning they override any built-in stylesheet the user has set up in the browser. (This could also be a trick to divert attention from the rest of the contents of the file.) Some of the links in this file have code like this attached to them:

onmousedown="javascript:void(myImage = new Image());void(myImage.src = \'(a PHP URL with some query string parameters)\');"

This is pretty obviously click-tracking. Ignore the use of an Image object here; the important part is to generate a GET from the browser to that URL whenever someone clicks down on the link. There's also more conventional calls to a JavaScript function urchinTracker from within onClick handlers.

There are some foreign-language strings visible in the text, too: a quick check with Google Translate found that they were, indeed, in Czech, reading something like this:

  • Sports betting on the Internet - Get up 1000 Kc!

  • Original gifts and gadgets for men and women!

  • ACTION! From November 14, 2011 fantastic prizes domain!

  • Mona furniture co. - furniture and special offers with 40% discount

  • Dedicated server for 450 Kc

  • Download and send files for FREE!

  • File download FREE!

Various sales pitches, in other words. ("Kc" is most likely the abbreviation for the Czech koruna, the local currency.)

To sum up: Classic spam E-mail, with a lot of deliberate obfuscation to try and evade spam-detection schemes. And who knows what other stunts this site is likely to pull, with all that garbage in the way?

I sent an E-mail to my friend warning her that her machine had been compromised, and she should either check it out or get it checked out. This would be a good time to point out that downloading and running just two programs will clear up almost any malware installed on a Windows system: Malwarebytes, and Spybot Search & Destroy. Also, make sure your antivirus is up to date. The More You Know.™

"Surfing safety."
"Keep breathing."
Roadkill and Y.T., Snow Crash, Neal Stephenson



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