Some people from outside Germany, where I’m from, would say that the Germans like correctness in business, love traditions and fear online transactions (or at least things that can’t be controlled). Well, what can I say… maybe they’re right, as some facts can speak for the above …
It has become an unwanted tradition for the German computing public to be receiving, for the last two years, threatening spam containing the file RECHNUNG.EXE. These “billings” typically referred to certain online orders of web cams, online shopping, furniture shopping, court invoices, payment of GEZ taxes, software licenses and more. The first time we’ve seen these kinds of emails was in April 2006, wherein the spam appeared to be an online invoice service setup by the German Telekom.
Taking a closer look at the text in the body we might assume that the social engineering used for this kind of attack is based on the fear that comes with online payment (generally based on the fear of errors related to uncontrollable and unexpected payments). The detection during the years 2006 and 2007 was as TROJ_YABE and TROJ_BZUB (ipv6monl.dll). In the second half of year 2007, the waves of the TROJ_YABE threat seemed to flatten or even stop. But after more than two years, it seems that the YABE Trojan is making a comeback.
In the last four weeks German users have been receiving “payment reminders” in their email inboxes. The evidence for the payment was either as attached file or as an accessible URL (named as “Rechnung.exe” or “Rechnung.pdf.exe” or variations of it). The spam run is still ongoing as of this writing. The payment notification was sent by a random sender address and it claimed to come from PayPal (Europe). This time the “invoice” was an archive file: Rechnung.rar (which contained the file Rechnung.exe). A sample email is shown below.
Upon execution the Trojan file (TROJ_BUZUB.IB) connects to a remote system and downloads a file (bot.exe or back.exe or variations of these names having the size of 49,152 bytes and are detected as TROJ_BUZUS.BG). Additionally, it rolls out a new version of WSNPOEM malware – NTOS.EXE, which is detected as TROJ_WSNPOEM.AA. The said Trojan exhibits rootkit abilities by being able to hide itself by hooking the WH_MSGFILTER event. It works with the data files stored in %System32%wnspoem: audio.dll and video.dll.
It also attempts to inject malicious code into svchost.exe and winlogon.exe services registering the targeted system remotely using the computer name and a certain ID. The malicious dll name used for the injection (at least in its version from 1st of June) is cryptonet.dll (28,672 bytes in size, and detected as a TROJ_BUZUB variant). A request to WHOIS database reveals that the IP of the download server belongs to a private person, which is currently being checked as of this writing.
