First forensics work - Part 2: Sure it's big enough...but look at the location

So you've managed to calm your nerves some. As we discussed in Part 1 of this series, you managed to collect memory and disk images from computers you could walk up too and touch using Helix. You have external hard drives filling up with images to be looked at. You have been going down the list of systems that you need to image and things are going smoothly.

Until now.

You have discovered, things are slightly more complex for the next system. One of the computers you have to take an image of is located in Seattle.

Nice city. Space Needle webcam is cool. OK weather, if you're a duck. They do call it the Rain City for a reason.

But there is just one small problem.

You are in Cleavland. Why, I'm not sure, but you are. And in Seattle you have an office of 10 people, and nobody there is really technical, and you can't ask anyone there to help out.

First thoughts: Have plane, will travel!

Second thought: Ya right... as if the boss will go for that.

Now you start to think to yourself "How the heck am I going to get that image from Seattle?". How indeeed. The plane thought would be easy, as then you could just use Helix when you get on site. But that would not be the most effective use of your time. So you sit back and take stock of what you have:

• Is there a network connection between here and there? Yup, a dedicated pipe. Good.
• Are network accounts used in Seattle? Yup, everyone uses the corporate AD. Good!
• Do you have a known good source for your tools on a CD? Yup, you have your Forensics 508 course DVD at your desk. Extra good!
• Can you have a domain administrator account created for you? Yup, you have authorization. Really good!
• Is there a laptop or stand-alone system you can use? Yup, you have a laptop at your desk. Excellent!

That's about all you need. And, depending on the speed of your links, you may need just a little bit of patience and time.

In order to start imaging on a remote system, I personally like to have a command shell on that system. Is it needed? No, but it's my preference. You could do this through psexec, so choose your own preference.

I start by loading up my 508 DVD in a stand alone system and share out the DVD. I also put in a USB HD on this system and share it. Normally I try to use a laptop that isn't joined to the domain. Why you ask? I prefer this, as domain policies and corporate software can sometimes cause issues , so I like to remove that as a potential source of problems. You also can easily disable any software that you need to on a stand alone system. Not necessarily as easy with a GPO controlled system.

I also prefer a stand alone system for another reason. If needed or I'm concerned about possible infection/compromise on that computer, it gets re-imaged . And it isn't the system I use every day and have all my tools configured on.

After sharing out the drives, I launch a command prompt from the course DVD. This is located in D:\IR\<Windows OS> which is the OS of the system you need to have the command shell on. This is done from an administrator account I have logged into this system with.

After launching the command shell, I then run the cmdenv.bat file that is also on the course DVD. This is a quick batch file that sets up the paths to run only the tools from the DVD and not from the underlying OS. Once I have the command shell on my local system, I run the following command to get a shell on the remote system

psexec —u user —p pass \\remote_ip cmd "/C net use x: \\local_ip\cdrom & x:\ir\<windows OS>\cmd.exe

• user the username domain administrator account you had created
• pass the password of this account
• "remote_ip" the IP of the system you wish to have the command shell launched on
• "local_ip" the IP of the local computer you are working on and have the DVD shared on
• <windows OS> the os of the system you are connecting to (e.g. if it is a Windows 2k server, use 2k)

This should open up, barring any problems, a command shell for you. You now are on the remote system, so remember everything you type is leaving a footprint there. I run the "cmdenv.bat" script within this remote system shell, and then I normally map over the USB HD I shared out from laptop next, by using the net command.

net use z: \local_ip\hd

Now before increasing the footprint much more, I do a memory image with the "win32dd.exe" or "win64dd.exe" program, located on the FOR508 DVD as well. To do this, run

win32dd.exe /f z:\memory_image.img

Then you should have appearing across the network, a memory image of the remote system. After this is completed, I then run the dd command to get a copy of the hard disk. Remember though, that you will need to image EACH of the drive mappings (e.g. C:\ D:\ etc) on the system, instead of the entire physical disk. To image and send to the mapped drive you setup, run the following command

dd.exe if=\\.\C: of=Z:\evidence\disk_image.img —cryptsum md5 -verify -cryptout=Z:\evidence\disk_image.md5 -localwrt 

This will provide you with a copy of the local C drive, and store it out to your mapped Z drive, give you the MD5 hash of this image file.

After all this, you should have a copy of the memory image and the disk image for the remote system you were accessing. Some things to note with this process

• The username and password you use with the psexec will be passed over the network in clear text. So I recommend that you create an account that will be used only for this investigation and then disabled. Mike Pilkington goes into more details on psexec and some alternatives in his recent blog posting, so I recommend taking a look at that posting located here. You can also go and read more on the psexec webpage
• If your company uses personal firewalls or IPS sytems deployed, you may need to either white list the IP you perform your evidence acquisition from or disable these systems. The psexec command, etc. may not be allowed into the remote computer to start your evidence acquisition process. I find that whitelisting a static IP assigned to your IR laptop removes the issue and avoids having to shut down protection measures when you don't have the time.
• As mentioned in Part 1, make sure you keep excellent notes on what you are doing, what commands you are running and on what systems. You'll need this later on when you are doing analysis.

If none of the above is working, or if you don't have access to the remote at all, then all you can really do is get the hard disk sent to you so you can image it once you have it with a USB to SATA converter (or whatever drive format it is). No you won't have the memory image of the system, but at least you'll have something to work with.

Is this the only way to do this work? Not at all. You could use netcat, Helix with listeners, and probably a dozen other ways. But this is what works for me.

Does your head hurt? Don't worry. This takes time especially if you are just starting out. If you've taken 508, go back and look in your Day 2 book, this is where this is covered.

Next up, Part 3, starting some analysis.

Jonathan works as a Senior Technical Specialist in IT Security for the Canadian federal government. He is a SANS mentor, a GIAC question writer and he holds numerous certifications including GCFA and GWAN. When not working, his spare time is filled by his 3 young daughters.