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 information...an excerpt of the output appears below:

G:\book2\DVD\ch4\code>pnu.pl d:\cases\ntuser.dat
LastWrite time = Mon Sep 26 23:33:06 2005 (UTC)
Mon Sep 26 23:33:06 2005 (UTC)
UEME_RUNPATH
UEME_RUNPATH:C:\WINDOWS\system32\notepad.exe
Mon Sep 26 23:26:43 2005 (UTC)
UEME_RUNPATH:Z:\WINNT\system32\sol.exe
Mon Sep 26 23:22:30 2005 (UTC)
UEME_UISCUT
UEME_RUNPATH:Downloads.lnk
Mon Sep 26 23:16:26 2005 (UTC)
UEME_RUNPATH:C:\Program Files\Morpheus\Morpheus.exe
Mon Sep 26 23:16:25 2005 (UTC)
UEME_RUNPATH:Morpheus.lnk
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)
UEME_RUNPATH:d:\bintext.exe

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 CLSIDs...one 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.