Internet Firewalls

July 1996


Internet Firewalls

Routers and gateways help keep cyberbandits off the data superhighway.

Although the Internet was designed as an easy way for computer users to exchange information, it has turned into a major security headache for federal agencies trying to protect private networks from hackers. Internet-based data can be altered by anyone with a PC and enough skill and determination to crack passwords. A couple of years ago, for instance, a group of Danish teenagers used the Internet to gain access to the National Weather Service's main computer network and almost succeeded in shutting it down and grounding commercial airlines that depend on the center's forecasts.

The incident highlighted the vulnerability of Internet-based data and prompted many federal agencies to begin installing firewalls to guard against intrusion. Firewalls generally consist of a combination of hardware and software components that shield Web sites, e-mail and electronic-commerce transactions from intruders either inside or outside an agency.

Firewall products residing between internal and public networks monitor traffic and limit access only to authorized users. They are available from companies such as Digital Equipment Corp., Harris Computer Systems, IBM, Sterling Software, Telos and Trusted Information Systems. Prices range from $5,000 to $35,000 per system.

Several approaches exist to building firewall architectures. Some products incorporate special routers that use packet-filtering techniques to identify source addresses of users trying to enter networks. Routers can be programmed to deny access to unauthorized traffic and some can send out message alerts when suspicious activity is detected.

Other firewall products rely on gateways-connections between different networks-that oversee traffic, authenticate users and control access. Secure computer gateways known as proxy servers, installed between specific applications or agency work groups, can be programmed to hide critical information from outsiders. Like all firewall products, gateways can be difficult to maintain and therefore require coordinated management and technicaltrategies at all organization levels.

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