Dear Mr. Brent:

I've tested four of the popular personal software firewall products 
(ISS/NetworkICE, McAfee, Symantec, and Zone Labs) and found that they work 
okay in most cases.

When I oversaw tests about 2 years ago, I found interoperability problems 
with McAfee Personal Firewall and Symantec Norton Internet Security ONLY 
when used in conjunction with a VPN client (such as those from 
Altiga/Cisco, Check Point, or Nortel).  The companies were notified of the 
problems, so the difficulties may have been addressed.  However, I no 
longer consult at that company were I did the tests and therefore lack 
access to its controlled laboratory environment to carefully retest 
them.  BlackICE Defender and ZoneAlarm did not exhibit such difficulties 
during those tests.

To keep up on the technology, I have purchased and loaded versions of 
BlackICE, ZoneAlarm, and Norton Internet Security Family Edition on my home 
personal computers.  I have yet to experience a problem with any of 
them.  If I had more machines, I'd get the McAfee Personal Firewall and 
Tiny Personal Firewall to observe their behavior in a normal environment as 
well.

One of the benefits that I have found is that a personal firewall can be 
configured to ask permission to allow newly encountered outbound traffic 
from the computer.  I have been often amazed to find a commercial software 
product conducting undocumented communication to the Internet.  I have 
always forbidden such traffic until I can research and validate the need 
for it.  In most cases, I have not found a reason to ever allow such traffic.

Before the project was established to test both software and hardware based 
home firewall products began, my colleagues and I personally bought 
different ones to try at home.  I began with BlackICE Defender and access 
via a dial-up Mindspring account.  BlackICE alerted me to scanning even in 
that low-speed environment.  As a result of that initial experience plus 
the project test results, I strongly recommend that users of a high-speed 
broadband cable or DSL connection use a hardware router capable of Network 
Address Translation (NAT) to defend the access point plus software 
firewalls on all Macs and PCs on the home network.  I also believe that 
corporate computers should have the software firewalls installed on them.

I should also stress that an anti-virus product should be installed in 
addition to the software firewall, particularly a product that features an 
automated process to download new virus definitions.  Consider that the 
firewall may require a rule to allow such traffic to occur.

Note that any software firewall product, particularly in a corporate or VPN 
environment, may cause some difficulties when first installed.  Such 
difficulties are not problems with the product, which is functioning as 
intended.  Rather, the problems arise because many organizations are 
unaware of the types of information flows that are going on and have 
therefore not configured the software firewall to allow such traffic, 
particularly where a server will initiate packets to the client.  I have 
also found numerous cases were a vendor has done a poor job of identifying 
all of the ports (both TCP and UDP) that its product utilizes, which makes 
the configuration of any firewall (personal or corporate) to support the 
product somewhat of a chore.  I have also faulted many vendors for not 
registering their port usage with IANA (Internet Assigned Numbers 
Authority) or for using some other organization's registered port, an 
approach which could cause interoperability problems in the 
future.  Well-known ports are 0 - 1023 and registered ports are 1024 - 
49151.  For more information, see http://www.iana.org/assignments/port-numbers

Respectfully yours;
Marc Mandel

At 03:08 PM 05/03/2002 -0400, you wrote:
>Hi
>
>What is the biggest problem, with or pitfall of
>software firewalls that sit on the end user's PC
>or work station?  (meaning products like ZoneAlarm
>
>thanks
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