2.2. About Java Security Manager Policies

Security Policy
A set of defined permissions for different classes of code. The Java Security Manager compares actions requested by applications against the security policy. If an action is allowed by the policy, the Security Manager will permit that action to take place. If the action is not allowed by the policy, the Security Manager will deny that action. The security policy can define permissions based on the location of code, on the code's signature, or based on the subject's principals.
The Java Security Manager and the security policy used are configured using the Java Virtual Machine options java.security.manager and java.security.policy.
Basic Information

A security policy's entry consists of the following configuration elements, which are connected to the policytool:

The URL location (excluding the host and domain information) where the code originates from. This parameter is optional.
The alias used in the keystore to reference the signer whose private key was used to sign the code. This can be a single value or a comma-separated list of values. This parameter is optional. If omitted, presence or lack of a signature has no impact on the Java Security Manager.
A list of principal_type/principal_name pairs, which must be present within the executing thread's principal set. The Principals entry is optional. If it is omitted, it signifies that the principals of the executing thread will have no impact on the Java Security Manager.
A permission is the access which is granted to the code. Many permissions are provided as part of the Java Enterprise Edition 6 (Java EE 6) specification.