Q: Secure application using custom user rights

Hi there,

We're working on a project in Visual Basic .NET 2005 and the application needs to handle user rights internally. We're resolving the Windows user name, and we have a table with this user name linked to a group and rights per group etc. Now I can easity create a functional that returns true or false when it checks on whether the user has permissions to do something or not. But, now, when we compile and maybe use DOTFuscator or something similar, the user can still just change the IF command and get access... How do people handle this as a developer? What would be the best way to handle security internally?

Thanks,
Bob