Silicon Graphics Gauntlet, Administrator'S Manual, Page: 31 / 306

Understanding Gauntlet Firewall Concepts
5
Trusted Networks
Trusted networks are the networks inside your security perimeter. Trusted networks are
usually the ones that you are trying to protect. Often, you or someone in your
organization administers the machines on these networks. Your organization controls the
security measures for these networks. Usually, they are within the physical security
perimeter. They can also be connected by links you control in a Virtual Private Network,
as explained in Appendix C.
When you set up the firewall, you explicitly configure the networks your firewall can
trust. After initial configuration, the trusted networks usually include the firewall itself
and all networks behind the firewall.
Untrusted Networks
Untrusted networks are the networks outside your security perimeter. They are
untrusted because they are outside of your control or knowledge. You have no control
over the administration or security policies for these sites. They are the ones from which
you are trying to protect your network. However, you still need to and want to
communicate with these networks, even though they are untrusted.
When you setup the firewall, you explicitly configure the networks from which your
firewall can accept requests, but which it does not trust. By default, after initial
configuration, the untrusted networks are all networks outside the perimeter.
The firewall applies different policies (sets of rules) for requests from untrusted networks
than it does for requests from trusted networks. For some types of requests (including
TELNET, FTP, rlogin, rsh, and POP3), the firewall may use additional authentication
before processing the request. For others, the firewall may deny the request altogether.
Unknown Networks
Unknown networks are those networks that are neither trusted or untrusted. They are
unknown quantities to the firewall because you have not explicitly told the firewall that
this network is a trusted or an untrusted network. By default, there are no unknown
networks because the default list of untrusted networks covers everything that is not a
trusted network.