Question: The security policy under .NET is defined on four levels:
the enterprise level, the machine level, the user level and the application
domain level. Assume that all assemblies have full rights (that is, their
permission set is FullTrust) on the enterprise, the user, and
the application domain level. The security policy on the machine level is
defined as follows: see book
What rights does an assembly MSApp get, which comes from
Microsoft, is signed and was loaded from http://dotnet.jku.at/apps ?
To which code groups does it belong on the machine level?

Answer: see 3.8.1 Code-based Security, Determining the Rights of an Assembly

Assembly MSApp belongs to the code groups:

• all code
• Zone: Internet
• Publisher: Microsoft
• URL: http://dotnet.jku.at/*

... and thus receives the rights for the permission sets:

• Nothing
• Internet
• Microsoft
• SSW