[isapros] Re: ISA, Exchange 2007 and Perimeter Networks

From: "Greg Mulholland" <gmulholland@xxxxxxxxxxxx>
To: <isapros@xxxxxxxxxxxxx>
Date: Fri, 12 Jan 2007 09:11:18 +1100

Re: [isapros] Re: ISA, Exchange 2007 and Perimeter NetworksOh hell no.. please
dont! they are hideous
----- Original Message -----
From: Thor (Hammer of God)
To: isapros@xxxxxxxxxxxxx
Sent: Friday, January 12, 2007 6:41 AM
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

Hey Gerald- your last couple of posts all came in as base64 encoded text.
Was that on purpose? Just didn't want to approve the post if you were sending
out naked pictures of Steve or something...

On 1/11/07 9:09 AM, "Gerald G. Young" <g.young@xxxxxxxx> spoketh to all:

I always saw it as "initiation by fire". J

Cordially yours,
Jerry G. Young II
Product Engineer - Senior
Platform Engineering, Enterprise Hosting
NTT America, an NTT Communications Company

22451 Shaw Rd.
Sterling, VA 20166

Office: 571-434-1319
Fax: 703-333-6749
Email: g.young@xxxxxxxx

From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Thor (Hammer of God)
Sent: Thursday, January 11, 2007 11:46 AM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

"Overly poky." Kind of hard for me to argue with that one :-p

On 1/11/07 7:09 AM, "Amy Babinchak" <amy@xxxxxxxxxxxxxxxxxxxxxxxxxx>
spoketh to all:
Jason don't get discouraged. The changes in Exchange are monumental so
there are bound to be disagreements and changes of opinion on how to best
secure it. The concept of an authenticated access DMZ in a separate security
zone allowing only a very minimal set of protocols is a completely foreign
concept to 99% of firewall admins out there. That fact you are even thinking
about this stuff put you in an elite class. The rest are still poking holes and
setting up VLANs.

Tom, Thor and Jim can be a bit clubby and a little overly poky to new
comers. It's a twitch they developed after participating on the ISA server
mailing list. It got worse when they decided to join a general purpose SBS
list. I'm not sure that they'll ever completely recover.

Amy

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From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Jason Jones
Sent: Thursday, January 11, 2007 5:47 AM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

Wish I had never asked now...sometimes, some of you guys really don't make
it easy for new people to try express their views and pose questions for
comment without being slapped down. One minute I am being labelled as an
"idiot" for my comments/views, the next minute someone else who says the same
thing as me is now right and not challenged. What gives?

I know many of you guys don't know me from Adam, but kinda unfair to just
assume I know jack about ISA and secure network design just because I'm not
"part of the club".

Anyhow, thanks to Tim and Tom for seeming to share my disappointment with
the decision made by the Exchange 2007 team...I think I need to try and find
out how "official" their lack of support with 2k7 is going to be before I can
continue recommending the least privilege model I have been using for Exchange
2003.

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From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Jim Harrison
Sent: 11 January 2007 04:30
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
..maybe I'm just tired.
I spent two hours trying to get home tonight and I'm clearly not in my mind
(right or otherwise).
Forget I wrote and we'll start over tomorrow.

From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On
Behalf Of Thor (Hammer of God)
Sent: Wednesday, January 10, 2007 8:18 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

That's exactly what I'm talking about. And precisely the configuration I
deploy:

My FE is in the authenticated segment of the DMZ - and a member of my
internal domain; however, the "recommended protocols" the Exchange group
recommends are not necessary- and thus, Steve's contention that "CIFS and all
that other stuff... Might as well just be internal" I reject. I only allow
Kerberos-Sec, LDAP, LDAP GC, Ping and DNS only from my FE to the internal DC's.
And only HTTP to the BE's.

Even if the other prots WERE required, it would still be far smarter to
deploy the FE in the authenticated DMZ with limited access than to just give
full stack access to the ENTIRE internal network. This is a deployment of a
services made available (initially) to a global, anonymous, untrusted network.

Maybe I'm not properly articulating my point, but I have to say I'm really
surprised that we are having this conversation...

On 1/10/07 7:10 PM, "Jim Harrison" <Jim@xxxxxxxxxxxx> spoketh to all:
C'mon, Tim; I know what your deployment recommendations are; this isn't it.
He wants to extend his domain via "remote membership"; not create a
separate domain.

From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx]
<mailto:isapros-bounce@xxxxxxxxxxxxx%5d> On Behalf Of Thor (Hammer of God)
Sent: Wednesday, January 10, 2007 4:26 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

Because it's safer that way, that's why... That's what an authenticated
access DMZ perimeter is for- with a CAS server that presents logon services to
any Internet user, I would (and, in fact, require) that the server be in a
least-privileged authenticated access perimeter network that limits that
servers communications to the minimum required for required functionality - and
only to the hosts it needs to talk to.

Let's say there is a front-end implementation issue or coding
vulnerability: the CAS on the internal network would allow unfettered,
full-stack access to the internal network. A CAS in a perimeter DMZ would
mitigate potential exposure in the event of a 0day or configuration issue.

"Safer on the internal network" is a complete misnomer when it comes to
servers presenting services to an untrusted network.

On 1/10/07 3:04 PM, "Jim Harrison" <Jim@xxxxxxxxxxxx> spoketh to all:
Why would you want to place a member of your internal domain in your DMZ,
fer chrissakes?!?
Hosting any domain member in the DMZ is a difficult proposition; especially
where NAT is the order of the day.
You can either use a network shotgun at your firewall or attempt to use
your facvorite VPN tunnel across the firewall to the domain.

Jim

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From: isapros-bounce@xxxxxxxxxxxxx on behalf of Jason Jones
Sent: Wed 1/10/2007 2:35 PM
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

From what I can gather, the new CAS role now uses RPC to communicate with
the back-end (not sure of new name!) servers so I am guessing that this is an
"RPC isn't safe across firewalls" type stance. Which I guess for a PIX, is a
pretty true statement.

Just think how much safer the world will be when firewalls can understand
dynamic protocols like RPC...maybe one day firewalls will even be able to
understand and filter based upon RPC interface...maybe one day... :-D ;-)

Shame the Exchange team can't see how much ISA changes the traditional
approach to DMZ thinking...kinda makes you think that both teams work for a
different company :-(
Jason Jones | Silversands Limited | Desk: +44 (0)1202 360489 | Mobile: +44
(0)7971 500312 | Fax: +44 (0)1202 360900 | Email: jason.jones@xxxxxxxxxxxxxxxxx
<mailto:jason.jones@xxxxxxxxxxxxxxxxx>

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From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx]
<mailto:isapros-bounce@xxxxxxxxxxxxx%5d> On Behalf Of Greg Mulholland
Sent: 10 January 2007 22:07
To: isapros@xxxxxxxxxxxxx
Subject: [isapros] Re: ISA, Exchange 2007 and Perimeter Networks

I seriously hope that they have take different paths and these are not
limitations on the software or it is going to mean a nice little redesign and
break from custom..

Greg
----- Original Message -----
From: Jason Jones <mailto:Jason.Jones@xxxxxxxxxxxxxxxxx>
To: isapros@xxxxxxxxxxxxx
Sent: Thursday, January 11, 2007 8:25 AM
Subject: [isapros] ISA, Exchange 2007 and Perimeter Networks

Hi All,

I heard today from an Exchange MVP colleague that members of the Exchange
team (Scott Schnoll) are saying that they (Microsoft) do not support placing
the new Exchange 2007 Client Access Server (like the old Exch2k3 FE role) role
into a perimeter network. Has anyone else heard the same? This sounds very
similar to Exchange admins of old when they didn't really understand modern
application firewalls like ISA could do - RPC filter anyone???
http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&q=cas+dmz+isa&rnum=2&hl=en#4db165c21599cf9b

<http://groups.google.co.uk/group/microsoft.public.exchange.design/browse_thread/thread/4ecab9cb8e50015e/4db165c21599cf9b?lnk=st&amp;q=cas+dmz+isa&amp;rnum=2&amp;hl=en#4db165c21599cf9b>

I have just about managed to convince Exchange colleagues (and customers)
of the value of placing Exchange FE servers in a separate security zone from BE
servers, DC's etc and now I here this.

Are the Exchange team confusing the old traditional DMZ's with what ISA can
achieve with perimeter networks?

From what I believe, it is good perimeter security practice to place
servers which are Internet accessible into different security zones than
servers that are purely internal. Therefore, the idea of placing Exchange 2003
FE servers in an ISA auth access perimeter network with Exchange 2003 BE
servers on the internal network has always seemed like a good approach. It also
follows a good least privilege model.

Is this another example of the Exchange and ISA teams following different
paths????

Please tell me that I am wrong and that I am not going to have to start
putting all Exchange roles, irrespective of security risk, on the same network
again!!!!

Comments?

Cheers

All mail to and from this domain is GFI-scanned.

Follow-Ups:
- [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
  - From: Steve Moffat

References:
- [isapros] Re: ISA, Exchange 2007 and Perimeter Networks
  - From: Thor (Hammer of God)

[isapros] Re: ISA, Exchange 2007 and Perimeter Networks

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