However, the purpose of this article is not to discuss pros and cons of Themida or any other protector, nor do I have any intention to disgrace any of the software vendors. The purpose is to describe a relatively easy way of bypassing common anti debugging tricks (including Windows DRM protection) with DLL injection.

Internet is full of programmers forums and those forums are full with questions about CreateRemoteThread Windows API function not working on Windows 7 (when trying to inject a DLL). Those posts made by lucky people, somehow, redirect you to the MSDN page dedicated to this API, which says: "Terminal Services isolates each terminal session by design. Therefore, CreateRemoteThread fails if the target process is in a different session than the calling process." and, basically, means - start the process from your injector as suspended, inject your DLL and then resume the process' main thread.

Sometimes, a need may rise to start a thread in a separate process and the need is not necessarily malicious. For example, one may want to replace library functions or to place some code between the executable and a library function. However, Linux does not provide a system call that would do anything similar to CreateRemoteThread Windows API despite the fact that I see people searching for such functionality.

I doubt whether there is anybody in either AV industry or among reverse engineers who does not know what a software packer is. Malware research and reverse engineering forums are full of packers' related questions, descriptions thereof, unpacking suggestions and links to both packers and unpackers. In short - people have been doing a lot of precious work on defeating packers and protectors.

So. Executable code injection. In general, this term is associated with malicious intent. It is true in many cases, but in, at least, as many, it is not. Being malware researcher for the most of my career, I can assure you, that this technique appears to be very useful when researching malicious software, as it allows (in most cases) to defeat its protection and gather much of the needed information. Although, it is highly recommended not to use such approach, sometimes it is simply unavoidable.