Wednesday, August 29, 2007

TechTalk Interview

Back on 10 June, I did an interview on TechTalk, and I saw today that it's posted here. There's some other news...CNN, weather, etc...before the actual interview.

Check it out, give it a listen. Also be sure to check out some of the other shows in the archives.

Tuesday, August 21, 2007

Vista IR

I recently started doing some testing of IR tools on Vista, using Vista Ultimate (32-bit) installed into a VMWare Workstation 6.0 virtual machine.

Part of my testing involved running some tools on Vista to see how they worked, and another part involved mounting the *.vmdk file for my Vista VM using the latest versions of VDK and VDKWin.

IR Tools
I started off by downloading (via IE7) a couple of tools...specifically Autorunsc.exe and Tcpvcon.exe. Both seemed to work quite well, the only real hiccup being the GUI EULA dialog that pops up if you run the tools without the "/accepteula" switch (either way, the tools create a Registry sure you understand and document this as part of your IR methodology if you're using these tools). An interesting part of the tcpvcon output was the amount of IPv6 stuff visible.

My next steps are to test additional tools, as well as the use of WMI-based tools.

Extracting Files from a Vista VM
Mounting the Vista VM as a read-only file system/drive letter on my XP system went off without a hitch. I was already in the process of updating the VDK drivers and VDKWin GUI files, and on a whim I pointed the mount utility at the Vista VM *.vmdk file. I was pleasantly surprised to see the VM mounted as J:\. As expected, some of the directories (specifically, System Volume Information) could not be accessed...this is due to ACLs on those objects. However, I had fairly unrestricted access to the rest of the file system.

A friend mentioned to me recently that the offsets for the Last Run time and runcount in Vista Prefetch files is different from those of XP. I extracted a Prefetch file from the Vista VM and opened it in UltraEdit to look for the offset for the last run time. I found what appeared to be a FILETIME object at offset 0x80, and modified my existing code to extract those 8 bytes. The result matched up quite nicely:

C:\Perl> d:\hacking\
Last Run = Mon Aug 20 22:50:43 2007 (UTC)

I also tried running some of the Registry parsing tools (using the Parse::Win32Registry module by James McFarlane) against files extracted from the Vista VM. I started with a Perl script that would parse the contents of the UserAssist key - here's an extract of the results:

C:\Perl\reg> d:\hacking\vista_ntuser.dat
LastWrite time = Mon Aug 20 22:53:02 2007 (UTC)
Mon Aug 20 22:53:02 2007 (UTC)
UEME_RUNPIDL:%csidl2%\Accessories\Command Prompt.lnk
Tue Aug 14 18:47:55 2007 (UTC)
Wed Jul 11 20:37:27 2007 (UTC)

That seems to work quite nicely! It looks like I won't have any trouble accessing the raw Registry files using James' module, at least not on 32-bit versions of Vista, so that's good news!

There's still more testing and analysis to do, but this is a good start!

Saturday, August 18, 2007

Copying Files

I've been party to or heard a good number of discussions lately regarding USB removable storage devices, and one of the topics that invariably comes up is, how can you determine which files were copied from the system to a thumb drive, or vice versa.

In most instances, folks are working only with the image of a system, and do not have access to the thumb drive itself. They can easily find the information that tells them when a thumb drive was first connected, and when it was last connected...and then the next question is, what files were or may have been copied to the thumb drive (or from the thumb drive to the system)?

The fact is that Windows systems do not maintain a record of file copies or moves...there is simply no way for a forensic analyst to look at the image of a system and say which files were copied off of the system onto a thumb drive. In order to determine this, you'd need to have the thumb drive (or other media) itself, and be able to see that you had two files of the same or similar size (you can also compare the files with md5deep or ssdeep), one of which is on each piece of media. From there, you could then check the file MAC times and possibly make some conclusions regarding the direction of transfer.

Many times in a conversation on this topic, someone will bring up Windows shortcuts or LNK files. To be honest, I'm not really sure why this comes up, it just seems to be the case. Shortcuts can be created manually, of course, but with regards to files, they are created when a user double-clicks a file, such as a Word document, to open it. Repeated testing on my part (including testing done by others) has yet to turn a method by which normal (as in "normal user activity") dragging-and-dropping a file or using the "copy" command will result in a Windows shortcut file being created.

Does anyone out there have any thoughts or input on tracking this kind of activity, having nothing more than a single system image to analyze? If so, I'd appreciate hearing from you.

Friday, August 17, 2007

IR "Best Practices"

I know it's been a while since I've posted, but work has been really keeping me busy...that's an excuse that we all use, but that's my story and I'm stickin' with it!

So, I've been talking to a number of different folks recently, having discussions during my travels to and fro about incident response and computer forensics. Many times, the issue of "best practices" has come up and that got me thinking...with no specific standards body governing computer forensics or incident response, who decides what "best practices" are? Is it FIRST? After all, they have "IR" in their name, and it does stand for "incident response". Is it the ACPO Guidelines that specify "best practices"?

Well, the easy answer (for me, anyway) is that "it depends". Funny, haha, I know. But in a sense, it does. "Best practices" depend a great deal on the political and cultural makeup of your organization; I've seen places where the incident response team has NO access to the systems, and must request data and information from the network operations staff, which has their own daily tasks and requirements.

But all that aside, we can focus on the technical details of responding to Windows systems. When we say "best practices", we can specify the information we need to get in order to properly assess the situation/incident, how to go about getting it (retrieve it locally, remotely, via live acquisition, via post-mortem exam, etc.), and in what order to retrieve that data (the ACPO Guidelines specify dumping the contents of physical memory last, rather than first...), etc.

For example, we know that during live response, anything we do is going to leave an artifact. So, why not specify what data you're going to collect and the method by which you're going to collect that data? Then determine the artifacts that are left through testing, and document your procedure and artifacts (hint: things like batch files and scripts can constitute "documentation", particularly when burned to CD), and implement that procedure via some means (ie, batch file, script, etc.).

One of the questions that invariably comes up during discussions of live response and "best practices" is, can data collected via live response be used as evidence in court? I would suggest that the answer is, "why not?" After all, an assault victim can be treated by EMTs, operated on by a surgeon, and cared for in a hospital, and the police can still collect evidence and locate and prosecute the perpetrator, right? It's all about documentation, folks.