A few months ago, we blogged about the banking trojan Retefe (Blog post in German) that was and still is targeting Switzerland. First off, Retefe is different because it only targets Switzerland, Austria and Sweden (and sometimes Japan). Contrast this to many other banking Trojans, which have a much more global and dynamic target list. Not only that, but the Retefe infrastructure also prevents computers from not affected countries to connect to its systems by using geo-location aware access lists and filters. The second unique property of Retefe is the fact, that it only modifies the operating system by adding a fake root certificate and by changing the DNS server for domain name resolution. After infection, the installer removes itself, which makes life hard for anti-virus software trying to detect a malicious Retefe component or activity.
Since a few days, Retefe is back again with a new twist. It still targets the same countries and the same banks. Not too exciting, the spam campaign has changed. However, in this wave Retefe is picky and only installs itself on selected computers. And some icing to the cake, it also installs another malware called DOFOIL. In this blog post, we give a technical analysis of the new Retefe.