As on today, even though there is quite a bit of overlap, there are some
significant
differences between IPS and Firewall technolgies. In future, vendors might
combine both
of these and call as IPS or by some other name.
In my view, Firewallsdo following, which IPSes don't do normally.
- Firewalls implement 'Access Control lists' , each list having set of
access control
rules and filtering happens based on these lists. These lists are
referred only
upon session establishment, not for each packet (IPS/IDS systems tend to
go through all the rules for evey packet, even though some intelligence
is built into
IPSes to intelligently select subset of rules for searching).
Firewalls today tend to stop search upon a rule match. In IPS/IDS
systems, all rules
are searched to ensure that there are no attack pattern associated with
the packet/data.
- Firewall are always 'Inline'.
- Firewalls do 'NAT', 'Port forwarding' and Redirection of traffic.
- Firewalls open holes by intelligently intrepreting the application data
(ALGs).
- Firewalls allow user/machine specific access by authenticating the users.
- Firewalls can do application filtering and gracefully shutdown the
connections by
sending applicaiton specific errors (pages and strings). Some firewalls do
this by
proxying (SOCKS5, HTTP Proxy, SMTP Proxy) etc..
Srini
----- Original Message -----
From: "Jacob Winston" <jctx09@yahoo.com>
To: <focus-ids@securityfocus.com>
Sent: Sunday, August 15, 2004 7:46 PM
Subject: Firewall vs. IPS - Differences now (ISS, Intrushield 2.1?)
Things are getting a little confusing. ISS claims that its Proventia boxes
are also firewallas. Intrushield 2.1 has firewall/layer
4 filtering capabilities now. If the Intrushield box layer 4 acls now then what
makes it not be equal to a firewall? What does a
firewall do that an IPS doesn't as long as the IPS can do layer-4 access lists?
Any info is apprecaited.
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