ExtraWork is a module used by classic Battle.net games intended to return system data to the server. It can be utilized for different purposes but most notably, for hack detection. During the connection process, the server sends ExtraWork as a signed MPQ that contains a DLL file which exports a function called ExtraWork. See the wiki for more details.
Pre-compiled binaries are available on the Releases page.
A C++11 compliant compiler with WinAPI and an implementation of the draft File System Technical Specification (ISO/IEC JTC 1/SC 22/WG 21 N4100) available should be able to compile this project.
ExtraWork is free and unencumbered software released into the public domain as specified by UNLICENSE.