Multilevel secure networking

The security administrator is responsible for defining the security levels and categories required in a multilevel secure environment. These become part of the set of security labels used to enforce mandatory access control policies when applications access resources on behalf of users. All of the systems enforcing mandatory access control policies in a multilevel secure network must have equivalent definitions of these security labels and the systems in the network to which they apply.

In the networking environment, the information that is being protected is the data being read and written through sockets. Sockets are opened and used by applications running under user IDs. In a z/OS® multilevel secure environment:

• Each user ID is permitted to use one or more security labels.
• Every job or login session is associated with a user ID.
• A user ID can use only one security label for each job or login session.
• The security label used is limited by the port of entry (source type and location) of the job or login session.

Applications can have read access to information from many sources that can have various security labels. This information might be commingled in the buffers used to write information to the network. TCP/IP treats all socket data buffers as having the security label of the writing task. All sockets are inherently read/write, so TCP/IP requires communicating partners to have equivalent security labels in a multilevel secure environment.