Unraveling GootKit’s Stealth Loader

Discovered in the wild in the summer of 2014, the GootKit banking Trojan is considered to be one of the more advanced banking Trojans active nowadays. It is used in online banking fraud attacks on consumer and business bank accounts mostly in European countries.

GootKit is an ongoing malware project that implements advanced stealth and persistency alongside real-time web-based activities such as dynamic webinjections, which it can display directly in the infected machine’s browser. GootKit affects the three most popular browsers: Internet Explorer, Mozilla Firefox and Google Chrome.

According to IBM X-Force research, GootKit is developed and operated by a small Russian-speaking cyber gang who does not share or sell the source code to others. Additionally, the malware keeps improving the anti-research techniques it uses to protect its internal secrets from prying research’s eyes.

In terms of its internal makeup, unlike most malware of its grade, GootKit relies very little on leaked source codes from previous generations. Aside from its borrowed Zeus Trojan webinjection mechanism, it is a private project that was written in node.js — a rather uncommon programming language choice for any malware to adopt.

Recent studies of this malcode conducted by IBM X-Force Research have shown that this family of malware is usually equipped with advanced mechanisms to detect virtual machines and well-known sandboxes. These are intended to stop the malware from running in those test environments.

GootKit’s security evasion begins in its stealth loader, and this is the component researchers Maksim Shudrak and Cindy Eisner of IBM Research — Haifa have analyzed in depth. Their research results are brought to you in a dedicated paper you can download directly on IBM’s X-Force Exchange. Please access the collection and check the sidebar on the right of your screen for the attached PDF.

Dear reader: this post is part of my research work at IBM X-Force. You can go to the original post here.