Re: ISA Server or Firewall Appliance?
From: Susan Bradley, CPA aka Ebitz - SBS Rocks [MVP] (sbradcpa_at_pacbell.net)
Date: 11/16/05
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Date: Tue, 15 Nov 2005 17:51:30 -0800 To: James Eaton-Lee <james.mailing@gmail.com>
The annoying SBSer with ISA on her box is going to challenge you on that
one.
What exactly doesn't feel quite right? Why does it not feel right?
In my network I like it because it's on a platform that I can monitor
easier. Control better. Patch easier. [WSUS will soon support ISA as a
matter of fact]
Isn't the same true for big networks?
I think we all need to let go of our OS perceptions and look at the
realities of operating systems these days and what not. If we can't
control it...understand it...I'm not sure it's not helping in the
security fabric of my network.
Our firewalls are not our perimeters any more.
James Eaton-Lee wrote:
> On Tue, 2005-11-15 at 11:58 -0500, Marcos Marrero wrote:
>
>> Hello to all,
>>
>> I have a question to see what everyone out there thinks. Here it goes...
>>
>> Is it better to have a firewall appliance (Checkpoint, Juniper, etc) or
>> is ISA server enough to use as a firewall (along with all of the other
>> options it provides)?
>>
>> Of course the ISA server would sit facing the internet, like a firewall
>> would and it would have to sit on a hardened machine.
>>
>> Just want to know what everyone out there thinks about this
>> configuration or idea?
>>
>
> What you have to bear in mind here is that an appliance is, generally, a
> hardware platform fairly similar to that which you might deploy ISA on
> top of, with a proprietary operating system (typically based on freebsd,
> or some other BSD-derived OS). Oftentimes these firewalls will run from
> flash memory rather than hard disks, but that aside there can be very
> few differences - I've seen more than one appliance (checkpoint being
> just one) based around a fairly standard ATX motherboard with an
> AthlonXP chip!
>
> Appliances have advantages in some instances and not in others.
>
> Specifically, due to the overhead of running ISA (which is harder to
> chop down to provide a subset of the capabilities of a simpler package)
> and a large, general purpose operating system, you'll almost find that
> an appliance will handle a greater load then ISA on a similar box,
> particularly if you're doing anything remotely intensive (although with
> modern hardware you'll frequently hit hardware limitations first).
>
> Arguably, due to the dedicated nature of an appliance, it's also securer
> as there are fewer running services, and there's more operating system
> hardening and more functionality gutted out of the operating system -
> less to go wrong, and less to exploit when something does.
>
> There are also disadvantages to appliances - they're, generally
> speaking, not designed to be administered in as comprehensive-a manner
> as their 'software' counterparts - meaning that when you do need to
> remove or add something it can be harder. This argument applies equally
> to adding NICs and, for instance, adding proxying capability.
>
> Specific to ISA, ISA is extremely flexible, and you'll probably find is
> far more capable of being deployed in different roles than, for
> instance, checkpoint. This is also a mixed blessing (as you don't
> necessary want ISA providing routing for your internet backbone, even if
> you can use it for this). It also benefits from domain integration, and
> (in my opinion), this is one of the most compelling arguments in its
> favour.
>
> You could also argue that if you want separation between different
> segments of your security strategy, this is a bad thing when compared to
> a set of checkpoint firewalls.
>
> You'll get a different argument on this from everyone (everyone has
> their favourite firewall), but hopefully that's outlined some of the
> broader arguments in favour of appliances vs. software firewalls.
>
> It's also worth looking (shudder the thought) at 'free' alternatives, if
> you're doing a comparison - and there are just as many different options
> here as there are in the commercial world, from the use of an operating
> system which provides routing/firewalling capability through
> kernel&userspace tools generally bundled with the OS (such as openbsd
> with pf, freebsd with ipfw, or linux with iproute2/netfilter) to an
> 'appliance' based on BSD or linux.
>
> The latter choice starts to become more appealing when you bear in mind
> that plenty of vendors (checkpoint, juniper and borderware being just a
> few) base their network devices on BSD (and some on linux, like
> linksys). It's another debate entirely what they add to bog-standard
> BSD, but the comparison is worth making.
>
> m0n0wall, ipcop, smoothwall and redwall are all worth looking at in
> these situations - m0n0wall being perhaps the most appropriate for
> deployments you may be looking at. They are worth at least looking at
> when in the commercial world, license fees are such a large
> consideration!
>
> The only last point I'd make is that I'd be hesitant in deploying ISA in
> an internet facing role (although I do and have done that before) - but
> I don't really have a justification for this aside from "it just doesn't
> feel quite right".
>
> Hope that helps! :)
>
> - James.
>
>
>> Regards
>> Marcos Marrero * Banking Officer * Data Security
>> Lloyds TSB Bank * US Information Technology
>> _________________________________
>> Tel: (305) 347-6421 * Fax (305) 371-8607
>>
>>
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