SynJunkie above gave a link with some keyloggers you can compile. The first place to start is to grab the source code and review it. Get as much source code out there and get a general idea of how loggers are coded. Then from there you can start to make changes. The idea is to change the source code until the sig is no longer detected. Now what might happen is , depending on how much you have to rewrite it, you lose some functionality and possible stability. It really depends on the quality of the code you are editing. But whats left might be all you need to get you a password and not be detected. This is the down and dirty way and is really more just "hacking up" the code. Advantages are its a fast way to do it and doesn't require a superior level of programming skill. On the other hand , if you are great at programming, you will take the time to write on from ground up making sure to approach it from a different angle than whats available.