| [Serializable] | 
1. Enterprise
2. Machine
3. User
4. Application domain
| AppDomain | Security policy for all managed code in an application. | 
| Enterprise | Security policy for all managed code in an enterprise. | 
| Machine | Security policy for all managed code that is run on the computer. | 
| User | Security policy for all managed code that is run by the user. | 
Hierarchy: