Firewalls: Packet-filtering and Application Proxy
For chapter 6

A firewall is a computer that acts as a barrier between computer systems on one "side" and computer systems on the other "side." For instance, a company might install a firewall between its own, internal network and the rest of the Internet (and world). The firewall would act as a filter for messages going between the internal network and the outside Internet. The internal network is therefore protected from the outside as the firewall will not allow messages or packets from unapproved sources to go beyond the firewall to the internal network. Therefore, a firewall can protect a company and its data from outside hackers, from misguided messages, and from unapproved employees.

There are two types of firewalls used by businesses and organizations: (1) packet-filtering and (2) application proxy. Packet-filtering firewalls are much faster than application proxy firewalls they base their decision of whether or not to let a message through merely on the header of the packet being transmitted. Application proxy firewalls are slower but much more secure because they evaluate the application layer of the transmission, thus gaining more information about it, and enabling a better decision. To take advantage of the speed of packet-filtering and the security of application proxy firewalls, Network Associates (http://www.nai.com/) has introduced their Guantlet Firewall 3.0 with Adaptive Proxy firewall technology that combines the advantages of the two separate technologies. Network Presence, a Los Angeles computer security firm, tested the new firewall and found it to be ten times faster than traditional application proxy firewalls, but with all the speed of a packet-filtering firewall. An additional feature of this new firewall is the ability to block spam, unsolicited e-mail sent to a mass mailing list that is seen as the equivalent to junk mail. More details can be found from Network Associates´ press release at http://www.nai.com/about/news/press/1998/october/101398b.asp.

Points to Ponder:

1. Visit the Network Associates web page http://www.nai.com/. What type of security system would you recommend were you to advise a small business owner? What would you recommend for a government agency? What are the options for home users?
2. Do you respond to spam the same as you would to junk mail?