Is it safe to replace some characters of a string resides in a DLL file using a Hex Editor? I'm not going to introduce new chars or remove any existing one, so the file size won't be changed. And what I am going to do is to replace some embedded SQL string which is written in lower-case, and make the chars of that string upper-case. Is it OK, or does it corrupt the DLL and make it unloadable? By the way, this DLL is not digitally signed with a code signing certificate.
unless the owner of the dll does some kind of validation of it, using a checksum for instance, it won't break anything.
(afaik most windows system dlls are watched somehow for modifications and windows will complain if you change them)