isr.co.ro : glossary Firewall A set of routines that attempts to provide an Internet host computer with certain types of connections to the rest of the Net without opening up that site to unauthorized uses or external attacks. Most large organizations that allow Internet access from their internal systems either have or are adding firewalls. Unfortunately, there's no way to guarantee the success of such a venture, and even the attempt to create an effective firewall can cause problems for some authorized programs.