RE: Sharing internet through Citrix (or better solution) in isolated network?

["Craig Wright" <Craig.Wright () bdo com au>]

In support of Ansgar's statement, there are some highly imaginative
exploits and methods to bypass data-diodes and other such system
switches. There are a couple of SANS instructors/authors I have met who
make a game of this. Further there is a large amount of research and
headway to breakouts for virtual machines in a similar (but far more
complex) manner to Choot breakouts of the past (and still occurring).

So complete isolation = separate systems and networks on separate - that
is not virtualised hardware. 

Regards,
Craig Wright (GSE-Compliance)



Craig Wright
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-----Original Message-----

From: listbounce () securityfocus com [mailto:listbounce () securityfocus com]
On Behalf Of Ansgar -59cobalt- Wiechers
Sent: Tuesday, 6 November 2007 3:47 AM
To: security-basics () securityfocus com
Subject: Re: Sharing internet through Citrix (or better solution) in
isolated network?

On 2007-11-05 Hamid . K wrote:
> I`m preparing solution for providing internet-access to internal
> users . What I`m looking for is a solution that completely isolate
> internet usage and internal systems.

If you want complete isolation of internet from intranet access you need
separate computers on a separate network running over separate network
hardware.

> I`m thinking about publishing internet through Citrix based solution,
> and keep everything restricted on citrix server/sessions.
> But I though there must be better solutions ,as using Citrix p.server
> for such case have it`s own security risks , some of them hard to
> skip ! 
>
> The good point about terminal based solution IMO is keeping user
> workstation clean and (almost) isolated, as it will act like a sandbox
> for running browser . 
> Any comments?

This scenario is known as a "graphical firewall". It's common practice
for allowing internet access from the workplace while keeping it in an
isolated environment. It's reasonably secure as long as you keep the
terminal server locked down (i.e. terminal server in a DMZ, no shared
files/printers between terminal server and LAN hosts, etc.)

> As always , open-source solutions (if any) are more welcome :)

VNC would be another option for building a graphical firewall, but it's
heavier on the resources than a Citrix (or Windows) terminal server.

Regards
Ansgar Wiechers
-- 
"All vulnerabilities deserve a public fear period prior to patches
becoming available."
--Jason Coombs on Bugtraq