There is no central server or centralized control by one individual, institution, or company. The beauty of open-source software is that you have the chance to verify all claims and you don't need to trust what I am saying or what the people before me wrote in this thread. You can go through the code and learn everything yourself. It's a completely different thing whether or not someone can do that, but that doesn't change the fact that such an option is available. Since most of us aren't developers and can't read code, you are stuck trusting those that can and have verified everything thoroughly. Since Bitcoin is very popular, you can be sure there has been plenty of scrutiny with more to come in the future.