Web Security and Commerce

Firewalls: Part of the Solution

A firewall is a device (usually a computer running a specially written or modified operating system) that isolates an organization’s internal network from the Internet at large, allowing specific connections to pass and blocking others. Ideally, firewalls are configured so that all outside connections to an internal network go through relatively few well-monitored locations. In so doing, firewalls are part of an organization’s overall security strategy.

Unfortunately, many organizations have seized upon firewall technology as their sole security strategy. We have seen organizations that realize they have serious security problems on their internal networks—and then attempt to “solve” this problem by simply using a firewall to block external access.

Because firewalls are frequently misused, we are ambivalent about them. We have too often seen firewalls as a substitute for real problem fixing. And because many attacks come from disgruntled or dishonest employees, and not from outsiders, firewalls divert attention from the real problems of network and host vulnerabilities, poor planning, and lack of organizational policies. Thus, firewalls often improve security only a small amount and, in the process, give their owners a false sense of security.

There are some real situations in which to use firewalls. One is that some organizations must use older "legacy systems” that cannot be secured: a firewall can be used to control access to these systems. (Such ...