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RE: tools used to examine a computer
From: "Robinson, Sonja" <SRobinson () HIPUSA com>
Date: Wed, 19 Feb 2003 15:18:28 -0500

In any event a BITSTREAM copy should be taken of any drive prior to analysis
if that is possible.  There are times when it is not.  Harlan has some good
points on processes, servies and the like.  You want to document those
before you take down a machine (workstation or server)anyway if you are able
to.  In the case of a server, you may not be able to take it down.  In that
case there are processes and analysis you can do without takin git down.
Also, there are tools that CAN do bitsream copies on LIVE machines.  That
being said.  If you can't take it down and you want to copy across a network
you can do that.  It does not destroy chain of custody (which is the term we
should be using) and you are not corrupting your evidence.  You may change
an access date (I did not test this and don't have time at the moment) but
you still have your modification and creation dates which won't change.  In
addition if you are following proper forensic procedures, all of this should
be documented (incl date and time) so you can prove that you did the copy
but it didn't modify.  I've done it and it will hold up.  Why would I copy
an entire 100GB serve to get one 100MB user share?  I could but you need to
do a costbenefit analysis before you do. IE. Is what in free, swap and slack
space potentially of enough interst to me to warrant that review since
potentially that amount can be HUGE.  A workstation can be different since
I'm not sorting through other users stuff and I can basically attribute all
or most of the files to a particular user based on profiles (assuming
Windows OS).    Key is proper FORENSIC PROCESSES are followed.  If you can
document and you are not touching MODIFY or CREATION dates then you are
pretty much OK as long as you document properly.   

-----Original Message-----
From: Trevor Cushen [mailto:Trevor.Cushen () sysnet ie] 
Sent: Wednesday, February 19, 2003 12:35 PM
To: security-basics () securityfocus com
Subject: RE: tools used to examine a computer


DD is not copying.  Copying can change file properties as in 
MAC details on the new system  or the destination.  The MAC 
being changed is the problem.  The original email I was 
answering didn't discuss documenting either or getting the 
MD5 signature.  DD will give a bit by bit copy which will 
give the same MD5 signatures and is handy if the machine 
cannot be rebooted.  The disk should be cloned before 
anything is done on the machine as in copying files or 
anything.  The document I refered to gave a way of doing that 
and is accepted by law enforcement once you have the MD5 signature.

Trevor Cushen
Sysnet Ltd

www.sysnet.ie
Tel: +353 1 2983000
Fax: +353 1 2960499



-----Original Message-----
From: H C [mailto:keydet89 () yahoo com] 
Sent: 18 February 2003 18:02
To: Trevor Cushen
Cc: security-basics () securityfocus com
Subject: RE: tools used to examine a computer


Also on the point of copying files over the network
first, correct me if
I'm wrong but that damages the chain of evidence.

Now so?  If one collects the necessary info (ie, MAC
times, NTFS ADSs, permissions, full path, etc), hashes
the file (MD5 and/or SHA-1), and then copies the file
over the network using something like 'dd' or type,
and netcat/cryptcat, how is the chain of evidence
broken?  Especially if it's documented?

Have a look at the
link below, goes about it a bit long winded but
essentially shows how to
clone a hard drive over a network connection.  This
can be done with
Windows machines as DD and Netcat can be run from
floppy on a Windows machine.

I'm not sure what you're getting at...first you make a 
reference to breaking the chain of evidence by copying a 
file, but then you talk about cloning an os over the network 
using dd and netcat.  Wouldn't doing so also break your chain 
of evidence, if your reasoning is to hold?

  


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