Home page logo

basics logo Security Basics mailing list archives

RE: Sharing internet through Citrix (or better solution) in isolated network?
From: "Craig Wright" <Craig.Wright () bdo com au>
Date: Tue, 6 Nov 2007 09:47:04 +1100

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. 

Craig Wright (GSE-Compliance)

Craig Wright
Manager of Information Systems

Direct : +61 2 9286 5497
Craig.Wright () bdo com au
+61 417 683 914

BDO Kendalls (NSW)
Level 19, 2 Market Street Sydney NSW 2000
GPO BOX 2551 Sydney NSW 2001
Fax +61 2 9993 9497

Liability limited by a scheme approved under Professional Standards Legislation in respect of matters arising within 
those States and Territories of Australia where such legislation exists.

The information in this email and any attachments is confidential.  If you are not the named addressee you must not 
read, print, copy, distribute, or use in any way this transmission or any information it contains.  If you have 
received this message in error, please notify the sender by return email, destroy all copies and delete it from your 

Any views expressed in this message are those of the individual sender and not necessarily endorsed by BDO Kendalls.  
You may not rely on this message as advice unless subsequently confirmed by fax or letter signed by a Partner or 
Director of BDO Kendalls.  It is your responsibility to scan this communication and any files attached for computer 
viruses and other defects.  BDO Kendalls does not accept liability for any loss or damage however caused which may 
result from this communication or any files attached.  A full version of the BDO Kendalls disclaimer, and our Privacy 
statement, can be found on the BDO Kendalls website at http://www.bdo.com.au or by emailing administrator () bdo com au 

BDO Kendalls is a national association of separate partnerships and entities.

-----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

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.

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

  By Date           By Thread  

Current thread:
[ Nmap | Sec Tools | Mailing Lists | Site News | About/Contact | Advertising | Privacy ]