Re: Firewall vs. IPS - Differences now (ISS, Intrushield 2.1?)

["Srini" <srao () intotoinc com>]

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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