How does implanting a backdoor into a DLL file differ from implanting one into an EXE file using The Backdoor Factory?

The main difference is that DLLs have export functions, which must be preserved for proper hijacking. The Backdoor Factory injects a payload into the DLL's code caves and modifies execution flow, similar to EXE files, but the payload must not break exported functions. If the payload disrupts stack balance, it can crash the DLL, as demonstrated in the article's debugging section. For more details on the EXE approach, see Implanting backdoors into EXE files using BDF.