One month ago David Barroso
visited one online banking user. David extracted one file from his mobile phone and I picked some ZeuS files up from his computer.This was the starting point of the so-called ZeuS MitMo
When ZeuS injects HTML code it usually asks the user for the necessary TANs in order to carry out a fraudulent transaction, but sometimes this information is not enough. Some banks ask for an additional code, sent by SMS, that the user (or criminal) must enter to finish the process. Until that moment this type of authentication (two-factor authentication) was successful, but not since then. This ZeuS gang had modified the configuration files to ask for the mobile phone number too. It's not so strange, but yes using it to commit the fraud. They sent to him an SMS with a link inside, telling the user that he should install that "certificate". When the user installed it, the malicious application
began to monitor all the incoming SMSs, looking for the bank SMS and forwarding it to the criminals. This way they already had all the information they needed to make the transaction, game over.
Apart of asking for the user phone number the configuration file had other curious things. When the user visited the online banking URL ZeuS added an script element to the legitimate web page pointing to an URL, avoiding to store all the HTML code in the config file. But this is not the strange thing, it's that normally the src attribute it's an absolute URL while in this case was a relative one:
curl_setopt( $curl_handle, CURLOPT_REFERER, sha1( $this->_key ) );
If the connection with the ZeuS panel was unsuccessful the PHP file returned this:
The ZeuS binary
related to this new configuration file was a version 184.108.40.206 with a low detection rate in the moment of the analysis. The general behaviour was the same as other binaries 2.0.x but it added a trick in the communication with the control panel. In order to download the configuration file it added X-Tag/53F54B2D
in the User-Agent
header. If this parameter wasn't present the file couldn't be downloaded.
Maybe the rumors about the merging of the source code of ZeuS and Spyeye are true, but I think we'll have to wait some time to see this new friend working alone, without another parallel developments. Why to buy a new trojan if the actual works perfectly fine?