How to block specific urls in objective-c?

Question

I searched the Internet for a way to block access to specific URLs in objective-c for OS X, but I only came across a method to modify the hosts file. This is not a good solution, since my application needs to regularly change blocked websites, and the host method requires an administrator password every time the application changes the file.

Does anyone know a way to block specific URLs other than the hosts file?

Thanks in advance, Rasmus.