While analyzing the components of Duqu, we discovered an interesting anomaly in the main component that is responsible for its business logics, the Payload DLL. We would like to share our findings and ask for help identifying the code.
Code layout
At first glance, the Payload DLL looks like a regular Windows PE DLL file compiled with Microsoft Visual Studio 2008 (linker version 9.0). The entry point code is absolutely standard, and there is one function exported by ordinal number 1 that also looks like MSVC++. This function is called from the PNF DLL and it is actually the “main” function that implements all the logics of contacting C&C servers, receiving additional payload modules and executing them. The most interesting is how this logic was programmed and what tools were used.
The code section of the Payload DLL is common for a binary that was made from several pieces of code. It consists of “slices” of code that may have been initially compiled in separate object files before they were linked in a single DLL. Most of them can be found in any C++ program, like the Standard Template Library (STL) functions, run-time library functions and user-written code, except the biggest slice that contains most of C&C interaction code.
Layout of the code section of the Payload DLL file
Constructor function for the linked list class.
This slice is different from others, because it was not compiled from C++ sources. It contains no references to any standard or user-written C++ functions, but is definitely object-oriented. We call it the Duqu Framework.
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