On Januaty 18 a colleague of mine (Luca) called me telling a malicious email was targeting Italian companies. This is the beginning of our new analysis adventure that Luca and I run together.
The email pretended to be sent by “Ministero dell’ Economia e delle Finanze” the Italian Department of Treasury and it had smart subjects such as:
The attacker knows very well the Italian Fiscal Year since those modules are very popular from company administration employees at that time. The attacker would probably exploit this attack path reaching out as many companies as possible. The email address was not coming from the “Ministero dell’ economia e delle Finanze” at all, it was coming from the following addresses:
The email looks like :
|Infection: Stage 1 Obfuscated|
|Infection: Stage 1 Clear Text|
A romantic “drop and execute” section was happening. A GET connection to 239outdoors.com/themes5.php was dropping a file named 1t.exe and later on the same script was able to execute the dropped file. The file 1t.exe was running on the victim machine contacting the Command and Control waiting for further commands.
The new sample looks like GootKit, a weaponized version of Banker Malware. The malware installs itself and contacts Command and Control asking “what to do” and sending the “stolen credentials” directly to the Command and Control server. Details on IPs, Persistencies and so on, is provided in the IoC section, but today’s we won’t describe GootKit, we got access to the Dropping site!
We want to figure out if we might help victims to deactivate the malicious botnet by providing as much as possible details without focusing on the reverse the Malware per se since appears to be known.
By getting further analyzing the dropping website we immediately understood that the same URL was dropping another threat. The parallel threat the dropping website was spreading to the world was called “Nuovo Documento 2008” and it was a .bat file as follows.
|New Threat Stage 1|
That executable .bat file on a first stage opens up a browser pointing to a legitimate image but later on, it uses a notorious technique called “certutil for delivery of file” to drop and execute another file. This technique is well described here by carnal0wnage. Basically, the attacker uses the certutil.exe program do download a Base64 encoded payload, to decode it and to run it. This technique is very silent since the User-Agent of certutils.exe is not suspicious because it needs to connect outside the company networks to check certificates, so not much IPS rules on it. The dropped file name unslss.exe appears to be very close to the previously analyzed one (1t.exe) it contacts the same C&C and it behaves in a similar way. But again we won’t focus on reverse such a malware but rather we wont be able to reach the highest number of IoC to protect as much as possible the victims. By analyzing the Dropping website we founded that a significative number of connections had additional referrers, so we decided to focus our attention on how many DNS were pointing to such a domain. We did it and the result was quite impressive (please see the Dropping URLs IoC Section).
Following the research on the dropping website, we found an interesting log of all the connection coming from possible victims. We collected that log, and we built the following possible infection list (possible Victims). We won’t publish the Victims IP addresses but if you can prove you are legitimated by your company to ask that logs we can give you (for free, of course) the IP addresses we’ve found related to your company. A detailed list of possible infected networks follows.
Following the found IoC provided by the long “analysis journey”. I managed this analysis over the night, so I am sure there would be some imprecisions, but I preferred to speed up the entire analysis process to give the opportunity to block such infamous threat as soon as possible.
Hope it helps the community.
The original post published by Marco Ramilli on his blog at the following URL: