Re: session logging IDS

["David W. Goodrum" <dgoodrum () nfr com>]

Hmmmm, I would like verification that either Cisco or Intrushield (or 
any other IDS/IPS) can actually capture an entire session from beginning 
to end, when the alert was triggered somewhere in the middle, and that 
they can do it all the time.  Most Network IDS & IPS systems can capture 
the offending packet.  Many can capture the offending packet, PLUS the 
rest of the session (which is what we at NFR do).  I haven't seen any 
that can guarantee capturing the entire session from beginning to end, 
unless they were capturing EVERY session (regardless of whether 
something bad happened in that session).  Here's an example:

I login via ftp.  I stay logged in for 10 minutes, browsing around, 
downloading some large benign files, but doing nothing bad.  Then, I try 
to get /etc/password.  Boom I trigger an alert.  10 minutes of packets 
are long gone... potentially many, MANY MegaBytes of data have passed 
during a single session.  On a gigabit network, 10 minutes is an 
EXTREMELY long time.  Unless your IDS or IPS is recording EVERY SINGLE 
packet for great lengths of time, to a hard disk somewhere, it will be 
all but impossible to go back in time and recreate the full session from 
beginning to end.  Starting recording from triggertime is easy, and I 
believe a lot of IDS and IPS systems do this.


Having said that, it IS possible to use some third party utility to do 
something similar to what you want, but even then there's still no 
guarantee: TCP sessions can stay open for hours and hours if necessary.  
For example, I can setup a box to do nothing but run tcpdump on the same 
wire I am doing IDS/IPS on, with a huge hard drive.  Let's say a 128GB 
drive.  If I'm monitoring a fully saturated 100Mbps, I will fill up that 
hard drive in just under 3 hours.  I can easily keep a session open for 
3 hours before doing something... "bad".  Plus, as network speeds 
increase, you will not be able to write your raw network data to that 
hard drive fast enough (or read it fast enough if alert rates are high.

-dave

David W. Goodrum
Senior Systems Engineer
NFR Security, Intrusion Detection & Prevention
http://www.nfr.com





Raj Malhotra wrote:

> Hello all,
>
> We are evaluating available NIDS products which would work at 100 mbps
> and would also do "session logging". By "session logging", we would
> want the IDS to log the "entire session" and not just the session
> "after" an intrusion is detected.
>
> We saw a couple of IDS which would probably be able to do something like this,
> Cisco IDS
> Intrushield
>
> Cisco offers session logging as well as replay.
> Intrushield says something like "Highly customized capture of
> individual packet, individual session, specific source/destination, or
> entire traffic stream upon attack detection" which might be translated
> as "logging of the session only after an attack has been detected".
>
> Can anyone tell us more about these or any such IDS that are available
> which can  log the entire session.
> Also, has anyone used any of these and with what degree of success?
> You can mail us back off the list if you so wish so.
>
> thanks
> Raj
>