[Lazy]

Code injection is not just used for hacks, basically you force a remote process to call LoadLibrary with your dll using CreateRemoteThread.

Once created, you call WaitForSingleObject on the remote thread and get the result of LoadLibrary with GetExitCodeThread.

Once the dll has been loaded by the remote process it becomes part of the application.
Calling GetModuleFilename in DllMain under DLL_PROCESS_ATTACH and displaying it with a message box will show the name of the application you injected the dll into.