Thursday, February 15, 2007

(In)Secure Magazine Mention

I received an email from Didier Stevens this morning, letting me know that he'd mentioned me in an article that he wrote for (In)Secure Magazine (issue 1.10, Feb 2007). His article, "ROT-13 is used in Windows? You're joking!" starts on pg 72 of the PDF, and runs through pg 77, where he mentions my ProScript.

Didier's article is on the use of ROT-13 to "encrypt" information that Windows uses to keep track of most frequently used programs (MFUPs). These MFUPs are tracked in order to populate the new Start menu, in both the pinned list (left side) as well as the most frequently used programs list (at the bottom)...see Didier's article for the full explanation.

The ProScript that Didier mentions is a Perl script (go figure, right??) that works with Technology Pathway's ProDiscover forensic analysis product, and parses the NTUSER.DAT files for all of the users on the system, extracting and "decrypting" the UserAssist entries and sorting them in order based on the timestamps that Didier mentions in his article. The ProScript is run against an image that is open in ProDiscover.

I also use a Perl script that parses the raw NTUSER.DAT files, and collects the same excerpt of the output appears below:

G:\book2\DVD\ch4\code> d:\cases\ntuser.dat
LastWrite time = Mon Sep 26 23:33:06 2005 (UTC)
Mon Sep 26 23:33:06 2005 (UTC)
Mon Sep 26 23:26:43 2005 (UTC)
Mon Sep 26 23:22:30 2005 (UTC)
Mon Sep 26 23:16:26 2005 (UTC)
UEME_RUNPATH:C:\Program Files\Morpheus\Morpheus.exe
Mon Sep 26 23:16:25 2005 (UTC)
Mon Sep 26 23:15:04 2005 (UTC)
UEME_RUNPATH:C:\Program Files\Internet Explorer\iexplore.exe
Mon Sep 26 23:04:08 2005 (UTC)

The UserAssist keys record user activities that are performed via the shell (ie, Windows Explorer). The UserAssist key actually has two subkeys, both of which are GUIDs or for the Active Desktop, and the other for the Internet Toolbar. If you've installed IE 7.0, you will see a third subkey.

Both the ProScript and the Perl script mentioned here will be available on the DVD that accompanies my next book, Windows Forensic Analysis, due our later this spring from Syngress/Elsevier.

Didier's got some other very interesting posts on his blog, so be sure to check it out when you get a chance.

Wednesday, February 14, 2007

BlackHat DC

Who's going to BlackHat DC? I found out today that my publisher has a pass available for me, and I'm looking forward to the opportunity to attend (hopefully, at least the first day of the briefings). It's been a while since I presented at BlackHat (2002, 2004), and the Forensic track looks like a good reason to go back!

Friday, February 09, 2007

Why I like Perl for Forensic Analysis

Many times when I post to a list or give a presentation and talk about using Perl, I almost immediately hear comments back such as, "I can't do that because I don't know Perl".

Well, I have to say, it's not about knowing Perl, or how to program, really. Most of the stuff I'm doing with Perl is translating binary stuff into something readable (timestamps, checking flag values), and just doing repetitive stuff. For example, in Windows Memory Analysis, I just use Perl to implement various processes that are repetitive and boring, and therefore I would be prone to making mistakes. The same is true with tools like SAMParse and SECParse that I use to parse the contents of raw Registry files. The information is there for anyone to see, extract, and interpret. I simply use Perl to do it automatically. In some cases, I write the scripts I do because there is commercial application that provides anywhere close to the information I want or need.

I have written tools to parse RAM dumps, parse Event Log .evt files (without using the Windows API), parse raw Registry files, etc. I wrote these tools because I needed them, and as it was very likely that I would need to do those things again, I automated the process in a Perl script.

I also hear things like, "I don't want to have to keep Perl up-to-date". I think in a lot of cases, comments like these come from folks who don't know a great deal about Perl...and you know...that's fine. It's okay, people. I'm not being a Perl snob or forensics snob or whatever snob, I simply use Perl to automate the repetitive tasks that make up my work day. Besides, I also use Perl2Exe, so all the tools that will be provided on the DVD that comes with my next book (Windows Forensic Analysis, from Syngress/Elsevier) will be provided with Perl "source" code, as well as a standalone EXE file that will allow you to run the tools on a Windows system without having to install Perl.

Perl is an interpretted language, so I don't have to "compile" my scripts to run them, and I can easily make modifications and changes to the scripts, updating or correcting them quickly. The scripts are somewhat self-documenting, although I do add my own comments to give myself a better view of what's going on, so I can figure out was I was doing a year or two later, rather than just look at it and think, "*I* wrote this??". Finally, Perl gives me a freedom and flexibility that is not available in commercial tools. For example, there are commercial tools that will allow you to view certain Registry data in a nice GUI, but you can only view that data, and only one entry at a time. With Perl, I can output multiple entries, as well as correlate data from multiple keys, such as when I want to show USB removable storage devices, any drive letters they were mapped to, and the last time each device was connected to the system (I should call this one "USBParse"). Don't like ASCII output in block format? In a few moments, I can have CSV style output. Ta-da!

So...some folks don't like to use Perl or open-source tools for forensic analysis, and that's okay. I use Perl because I know that if I have to perform some kind of analysis or correlation once, I'll probably have to do it again, and in order to avoid (as much as possible) forgetting a step or making a mistake, I'll automate the process.

Besides, I give most of this stuff away for free, as in beer.