Security in the .NET Framework
The common language runtime and the .NET Framework provide many useful classes and services that enable developers to easily write secure code and enable system administrators to customize the permissions granted to code so that it can access protected resources. In addition, the runtime and the .NET Framework provide useful classes and services that facilitate the use of cryptography and role-based security.
Effective with the .NET Framework version 4, there are major changes to the code access security system. Security policy is no longer applied to applications. All applications that can be run from the desktop are now executed as full-trust applications. This includes both applications on the computer and applications that can be run from a network share. Partially trusted applications must be run in a sandbox, which determines their grant set. The permission system continues to be used, but it is transcended by security transparency rules. For information about these changes, see Security Changes in the .NET Framework 4.