This is true to an extent. However it is far more likely that someone will use an exploit on the server in the DMZ than on the firewall its self. For example:
Lets say you have a linux box running iptables with three NICs as your firewall. Behind the firewall, in the DMZ you have a web-server running apache or IIS. Behind the firewall in the 'secure' zone you have your network (it makes little difference whats running on it). Whats more likely? That someone finds an exploit to use againt you linux box which isn't running any services and only forwards packets from one interface to another (and perhaps runs an IDS also) or that someone will use a guid 0 expoilt on apache. OK so now they own the box in the DMZ, big deal - the damage is contained, from your DMZ they shouldn't be able to see the rest of the network, at worst they might sniff the traffic to and from the DMZ, but they own it anyway so its not as if the sniffed traffic will do them any good. Now lets take the two NIC example. If the DMZ is exploited they can now sniff -all- the traffic between your network and the internet, which is arguably more valuable than being able to access your network. If your firewall is well configured then its unlikely to be the weak point with which to access any part of your network, your DMZ however is. On Tue, 2003-06-10 at 19:40, Depp, Dennis M. wrote: > I'm not sure how a tri-homed firewall can be just as secure as a two > firewall setup. Consider this: > > Hacker is able to penetrate your firewall and "owns" the box. In a > tri-homed firewall, they now have direct access to your internal > network. If this had been a two firewall setup, they would have to > compromise the second box as well. While this may not be an issue as > they were already sucessful in owning one firewall, hopefully you have > your intrusion detection system tuned to a greater degree of sensativity > in your DMZ. And you will be able to discover this second attempt. > > I do think tri-homed firewalls are a good solution, but they are not as > secure as a two firewall solution. > > Dennis Depp > > > > > -----Original Message----- > > From: Chris Berry [mailto:[EMAIL PROTECTED] > > Sent: Tuesday, June 10, 2003 2:21 PM > > To: [EMAIL PROTECTED] > > > > >From: "Des Ward" <[EMAIL PROTECTED]> > > >The second means that all traffic has to traverse your LAN > > to get to the > > >'Unprotected' DMZ systems and also could leave your internal > > LAN open to > > >attack. > > > > My ASCII drawing didn't come out very well it was supposed to > > represent a > > tri-homed firewall, which, to the best of my knowledge is > > just as secure as > > a two firewall setup. > > > > Chris Berry > > [EMAIL PROTECTED] > > Systems Administrator > > JM Associates > > > > "Gold is for the mistress - silver for the maid > > Copper for the craftsman cunning in his trade. > > "Good!" said the Baron, sitting in his hall > > But steel - cold steel is master of them all." -- Rudyard Kipling > > > > _________________________________________________________________ > > Help STOP SPAM with the new MSN 8 and get 2 months FREE* > > http://join.msn.com/?page=features/junkmail > > > > > > -------------------------------------------------------------- > > ------------- > > Evaluating SSL VPNs' Consider NEOTERIS, chosen as leader by > > top analysts! > > The Gartner Group just put Neoteris in the top of its Magic Quadrant, > > while InStat has confirmed Neoteris as the leader in marketshare. > > > > Find out why, and see how you can get plug-n-play secure > > remote access in > > about an hour, with no client, server changes, or ongoing maintenance. > > > > Visit us at: http://www.neoteris.com/promos/sf-6-9.htm > > -------------------------------------------------------------- > > -------------- > > > > > > > > --------------------------------------------------------------------------- > Evaluating SSL VPNs' Consider NEOTERIS, chosen as leader by top analysts! > The Gartner Group just put Neoteris in the top of its Magic Quadrant, > while InStat has confirmed Neoteris as the leader in marketshare. > > Find out why, and see how you can get plug-n-play secure remote access in > about an hour, with no client, server changes, or ongoing maintenance. > > Visit us at: http://www.neoteris.com/promos/sf-6-9.htm > ---------------------------------------------------------------------------- --
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