On Tue, Aug 29, 2006 at 09:31:38AM -0400, xelerated wrote:
Im posrting this to the pen-test group, rather than firewall or IDS
because it covers many areas.
Id like to see what the pro's think about capturing and storing packet
payloads from firewalls, ids, etc... everything rather than just
loggin the incidents.
Im trying to explain to my management how useful the payloads could be
if we were ever to
really need them, say from a forensics point of view.
To give another example, one time I was seeing lots of firewall drops,
I could tell what ports, src and dest. but no packet data. To everyone
involved it looked like a worm trying to spread.
Well in the end it wasnt, infact is was something that was nice to
know about, but it was not hostile traffic. But if I had been able to
see the payloads i could have seen the data request and known from the
start what it was, or was not.
What would be really great, is a whitepaper covering this, or enough
info/facts that I could throw one together.
thanks!
Chris
C|EH, CISSP
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If you can afford it this is a good idea. You probably want to do a
calculation on exactly how much disk space and the sustained throughput to
disk that are required to do this (hint, both are quite large and expensive
for anything much beyond a T1 type circuit :-)). Then you will be wanting to
be considering the security and privacy implications of this (think clear text
passwords, credit card numbers, other confidential data that you are now
proposing to take liability for keeping safe and unexposed on a continuing
basis ...).
Now that thats all said (and with the note that the same issues apply
to argus) you may want to take a look at argus (http://www.qosient.com/argus)
which is an ip auditing tool which captures netflow like data (and can be set
to capture the first 256 bytes or so of every connections data field.
Some example numbers from our ~35 meg per second commodity link which
say that for some 226 gigs of traffic the reduced argus output data amounted
to about 1.6 gigs of output from the argus sensor (which is much easier and
cheaper to store for long periods of time). A full capture of this (relatively
slow) link would be 226 gigs per day and getting that data captured and stored
on disk is likely to be quite expensive because you need a fast disk subsystem
and a fast (probably independent of the disk machine) capture machine that
can buffer in memory to survive disk writes on the storage box (which will
cause network packet loss on the network interfaces).
Sensor to collector bandwidth reduction is quite high. Take the last
24 hours on our commodity link. Input data was 226 gigs:
Traffic Summary From: Sun Aug 20 5:58:58 2006 To: Mon Aug 21 5:59:00 2006
226,872,311,907 Total 160,526,269,792 Out 66,346,042,115 In
and if I use 70 megs as an average file size (it varies from 51 to 82 megs
hourly across the period) thats about 1.6 gigs of argus output for 226 gigs
on the wire for around a 140 to 1 reduction in bandwith needed between the
sensor and the collector. So a 10 meg link would do fine at a gig and a 100 meg
backhaul should handle a full 10 gig link (if not a channel bonded pair of 100s
Finally some papers on how we and other people use argus.
http://www.usenix.org/publications/login/2001-11/pdfs/epp.pdf
http://www.malmedal.net/Malmedal_Master_Thesis.pdf
http://www.internet2.edu/presentations/jtvancouver/20050720-Argus-VanEpp.pdf
Peter Van Epp / Operations and Technical Support
Simon Fraser University, Burnaby, B.C. Canada
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