RE: ssh and ids

[<Peter_Schawacker () NAI com>]

Hi Marty, 

Since you were kind enough to mention us :-) I thought I would offer two
comments about what you wrote regarding SSL "key escrow" (is it really
"key escrow" when the key isn't handed to a third party?) and IDS/IPS.
First, remember that storing your web server's private key on an
external system is something that's done routinely with SSL
accelerators.  Hardware SSL accelerators are commonplace these days.
Second, we fully understand that folks are often squeamish about sharing
keys, so great care was taken to protect the private keys on the
IntruShield appliance.  We believe we have found the best possible
strategy for mitigating private key theft risk while eliminating the
SSL/NIDS "blind spot".  Through the use of public key cryptography, we
persist the key in such a way that one would need information that is
resident only in the sensor, along with information that is resident
only in the IntruShield Manager in order to recover the key. Having just
one or the other will not suffice.  I won't bore the list with the
details, but our implementation is described here: 

        
http://www.nai.com/us/_tier2/products/_media/sniffer/wp_encr_th_prot.pdf

Should an attacker root your web server, how safe will your private keys
be?  If your IDS/IPS can't handle TCP/443 to your production web
servers, you have a blind spot where attackers can operate unseen and
unhindered.  Which is worse, copying your web servers' private keys to
your IPS to prevent a web server compromise, or being blind to attacks
against those same servers?  Frankly, I can't think of a single IDS/IPS
product that is less secure than a typical web server.  Security is all
about trade-offs.  This is not a difficult one.

You also alluded to the problem of covert channels.  I believe that the
best protection against covert channels is to stop the attacker before
the back door is installed.  Failing that, a host based IPS/firewall is
the last, strongest line of defense.  

Peter Schawacker, CISSP 
IPS Technical Evangelist 
McAfee 
Office 760 200 4258 
Mobile 760 880 4258 
ps () nai com

-----Original Message-----
From: Martin Roesch [mailto:roesch () sourcefire com] 
Sent: Friday, June 18, 2004 5:54 PM
To: Runion Mark A FGA DOIM WEBMASTER(ctr)
Cc: focus-ids () securityfocus com
Subject: Re: ssh and ids


Hey Mark,

VENDOR ALERT: I'm a vendor and I'm going to talk about my technology.   
Please take my comments with an appropriate amount of sodium chloride.

Sourcefire's RNA product is capable of isolating/identifying layer-7  
protocols (including encrypted protocols) and tracking the flows.  For  
example, if you wanted to find SSH/SSL traffic that it being initiated  
from outside your network to inside, setting up a query (or automated  
reporting) is pretty trivial.  Hacker busts into your network and sets  
up an SSH server, RNA picks it up and can let you know that it detected

a new service and logs the flow data, etc.  Anyway, if you're  
interested in seeing a demo or talking more, let me know.

As far as IDS being able to do much with encrypted traffic, there's  
generally not much to do once the session goes encrypted.  You can  
setup rules in a system like Snort to differentiate between "allowed"  
and "everyone else" hosts talking to machines on your network pretty  
easily (and you can query RNA's flow data for the info too).

I know the NAI guys just released a mod to their sensors that allow  
them to do real-time SSL decryption if you're willing to escrow the  
private crypto keys on the box (shudder).  There's been talk of  
implementing the same sort of thing in Snort (ala ssldump) for a while,

but it's never come together...

       -Marty


On Jun 18, 2004, at 2:18 PM, Runion Mark A FGA DOIM WEBMASTER(ctr)  
wrote:

> Lets suppose the attacker is mildly sophisticated, and after making
the
> initial assault roots the box and installs a secure backdoor or two.

> Is
> there any IDS capable of isolating data it cannot read, except to
> monitor
> authorized port usage of a system or group of systems?  Not to  
> complicate
> the question, but when the attacker is using portal gates and all
> communications traffic is encrypted in normal channels how can an IDS
> participate?  Monitoring normal traffic patterns seems a bit slow for
> detection.
>
> -
> Mark Runion
>
>
> ----------------------------------------------------------------------
> -
> ----
>
> ----------------------------------------------------------------------
> -
> ----
-- 
Martin Roesch - Founder/CTO, Sourcefire Inc. - (410)290-1616
Sourcefire: Intelligent Security Monitoring roesch () sourcefire com -
http://www.sourcefire.com
Snort: Open Source Network IDS - http://www.snort.org


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