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RE: Remote Desktop Command Fixation Attacks

Security in depth is alive and well, thank you.  In fact, it is security
in depth that allows administrators to prevent this type of "attack" (if
we can actually make the stretch to call it that).

However, for the record, this is not an "attack."  You might as well
just email the target and ask for their password.  Or if you can get
them to open files, just send off a rootkit.  But let's ignore that for
now- let's pretend that somehow this is a magic attack--  This is where
security-in-depth comes in, and where the overall context of your post
is incorrect:

First off, you block .rdp files at the SMTP gateway (that by itself is
security in depth). Secondly, normal domain users don't RDP to external
hosts, so there would never be an allow rule for outbound RDP.  Even if
there was some need for off-lan RDP traffic from users, it would be on a
host-by-host basis and managed by the firewalls.  That, again, is
security in depth.

If your users are running XP, then the admin would prevent them from
updating to the 6.0 client anyway.  All you have to do in this case is
configure your RDP hosts to require TLS encryption based on a
certificate, and the client will not be able to connect at all if the
certificate is not in the trusted root certificates store.  Done.  If
you've got advanced users or have allowed 6.0 clients, then you ensure
that the client is set not to connect if authentication fails against
TLS secured hosts - of course, these people would be educated against
lame attacks anyway, so, done.  If you are running Win2k8, then you use
group policy to disable clients opening un-signed RDP files in the first
place, and again, be done.  Or just use TSGateway and require
certificates to log on - heck, they'd never make it past the gateway if
you didn't allow them.  Done part IV.  If you've got Vista clients, then
you'd also be using egress firewall rules in the "public" network
context blocking the outbound traffic, all configured with a single GPO.
I could go on, and on.

The point is that just because you have (amazingly enough) qualified
this attack as "highly successful" and "vicious" does not, in any way,
degrade the value of security in depth.  In fact, it is a perfect
example *for* security in depth in that regard:  if this "attack"
succeeds against anyone, it is not because security in depth does not
exist, it is because security in depth was not practiced.


-----Original Message-----
From: pdp (architect) [mailto:pdp.gnucitizen@xxxxxxxxxxxxxx] 
Sent: Wednesday, October 10, 2007 4:15 AM
To: full-disclosure@xxxxxxxxxxxxxxxxx; bugtraq@xxxxxxxxxxxxxxxxx
Subject: Remote Desktop Command Fixation Attacks


Security in depth does not exist! No matter what you do, dedicated
attackers will always be able to penetrate your network. Seriously!
Information security is mostly about risk assessment and crisis

When it comes to exploitative penetration testing, I relay on tactics
rather then exploits. I've already talked about how insecure Remote
Desktop service could be. In this post I will show you how easy it is
to compromise a well protected Windows Terminal or CITRIX server with
a simple social engineering attack and some knowledge about the
platform we are about to exploit.

The attack is rather simple. All the bad guys have to do is to compose
a malicious RDP (for Windows Terminal Services) or ICA (for CITRIX)
file and send it to the victim. The victim is persuaded to open the
file by double clicking on it. When the connection is established, the
user will enter their credentials to login and as such let the hackers
in. Vicious!

I have a more detailed explanation about the tactics behind this
attack. Because I don't want to spam people with tones of text, I just
included a link which you can follow. Hope that this is useful and at
the same time eye opening, not that it is something completely
amazing. But it does work and it works well.


pdp (architect) | petko d. petkov