Generic Security Services App. GSS-API peers establish a common security mechanism for security context establishment either through administrative action, or through negotiation. The firewall can provide packet by packet filtering of packets coming into the intranet or leaving the intranet. The firewall can decide which packets should be forwarded based on source, destination addresses and port using an explicitly defined policy . Regulating bandwidth allocated to a specific multicast group's traffic Their Mbone gateway is based on a modified multicast routing daemon.
Postfix uses multiple layers of defense to protect the local system against intruders.
Almost every Postfix daemon can run in a chroot jail with fixed low privileges. Postfix does not even trust the contents of its own queue files, or the contents of its own IPC messages. Postfix avoids placing sender-provided information into shell environment variables. Last but not least, no Postfix program is set-uid. Note that you should not use their machines for these exercises, but I think you will find this useful reading.