Even if I am working for Cisco, may I add the following inline
You should not confuse between:
- packet filtering routers i.e. plain Cisco or xxx routers
with cumbersome and intrecate access control lists
- a firewall component which use a more evolved inspection
technique like PIX or Firewall-1
At 09:29 4/06/97 +0100, Pedro Salgueiro wrote:
>Hi to all,
>I've been "watching" the discussion regarding the differences between
packet-filtering and application level firewalls. I believe that there are
>1 - Packet filtering firewalls are more difficult to manage (It is very
simple to mis-configure => less secure).
>It may be very complicated establishing rules.
True for routers, not true for components like PIX or Firewall-1. The
later are more protocol aware and thus ACL are much easier to configure
>2 - Packet filter systems are always routing packets (so "fail-open" may
occur). A well known contructor firewall crashed with a ping attack and
routed all the packets from the insecure network to the secure one.
True again for routers, but, false for PIX/FW-1
>3 - If you are using a packet filter system and you provide SMTP, HTTP,
etc. you cannot control what the users do with those protocols,i.e., you
open or close a port. Application level firewalls provide secure daemons
of those protocols.
True again for routers, but, false for PIX/FW-1. The later
have the knowledge of HTTP, SMTP, ... protocols and actually
analyse the traffic to make their decision.
Hope this helps
>Data General Portugal
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>"Don't take life too serious no one gets out alive!!!! :-)"
>* These are my own opinions and do not reflect those of the company *
>From: Mike Jones
>Sent: quarta-feira, 4 de junho de 1997 8:55
>To: mfiocchi @
it; firewalls @
COM; carlsonp @
>Subject: Re: PIX and Firewall-1
>Peter Carlson writes....
>> There are many comparisons made by datacomm, lan times, ziff-davis and
>> others. Keep in mind that both pix and fw-1 are glorified packet filters,
>> even though they have a fancy name for it. I wouyld stick with an
>> application level gateway. They are well accepted and known for being more
>Many things are known that aren't so. This claim comes by periodically
>in this forum, and I have yet to get an answer to this question: in
>whatway are application level gateways more secure than, say, FW-1 or PIX?
>There are certainly capabilities that can be provided via application
>proxies that can't be provided by any filter-based technologies, but what
>types of attacks are a FW-1 or a PIX vulnerable to that application
> Mike Jones
> Sr. Technology Advisor
> UNIFIED Technologies