Analysis Question

Didier Stevens recently posted a Python script that will create a .VBS script with an embedded executable. This kind of reminds me of the stories about MIT in the late '60's, when the freshmen would try to crash the server, and the admins wrote the "servercrash" script...to sort of remove the mystery and ability to claim bragging rights from the whole mess.

Didier's script presents an interesting opportunity...what would you look for if you were analyzing a system and trying to determine if something like this had been used? Any thoughts? Grab the Python script, maybe install ActivePython, and see what you come up with...

Memory Collection and Analysis, part II

Based on my last post, I wanted to throw some quick tests together and see how things worked out...here's the results of what I found...

So, first off, I wanted to run ManTech's mdd...or memdd.exe, as it were. That worked out very well...ended up with a nice output file after running memdd.exe (renamed to mdd.exe) version 1.1:

06/17/2008 10:51 AM 23,520 mdd.exe 06/17/2008 10:56 AM 3,210,854,400 test.dmp

Next, I ran winen.exe, the tool available from GSI, as part of the EnCase 6.11 install (yes, I am a "dongled", licensed user). As I was running this on a Windows XP SP2 system with 2.99GB of RAM (4GB on the board) and used the defaults in the configuration file (except for where I was required to make an entry), I ended up with a total of five .E0x files. I then opened the .EO1 file as an evidence item in FTK Imager Lite v2.5.1 and, as expected, Imager did not recognize the file system. However, Imager appears to have read the EWF header info just fine, because it recognized what I had entered into the config file.

So I then chose Create Disk Image from Imager's File menu item, and chose Image File from the Select Source dialog. During the process of selecting options, I chose to have Imager output the image in 2000MB files (as opposed to the default 640MB file sizes used by winen). This resulted in two image files (winen.001 and .002), which I then cat'd together using the type command on Windows into a single file (winen.bin):

06/17/2008 01:18 PM 2,097,152,000 winen.001
06/17/2008 01:19 PM 1,113,702,400 winen.002
06/17/2008 01:42 PM 3,210,854,400 winen.bin

Notice that the file size for the final winen.bin file is the same as the test.dmp file created using mdd. Very cool.

Now...what to do with it? Well, that's where Volatility 1.1.1 comes in...I grabbed ActivePython, installed it, and was up and running with Volatility 1.1.1 in no time! I was able to view the process list, run the 'dlllist' command to get modules and the command line for each process, etc...all very cool stuff. Volatility worked very well on both memory dumps...not just the winen/FTK one, but the mdd RAM dump, as well.

So what's next? Well, I'd like to see about digging a bit deeper into the dumps, including:

- As Moyix discussed, enumerating Registry hives (or just keys and values) from memory
- Run Andreas's PTFinder against the memory dump and develop graphs of the processes using Richard McQuown's PTFinderFE
- Attempt to do file carving via scalpel

Anything else? What's in your wallet? =)

Take aways from this...it's likely that like linen, winen.exe will show up on IR tools distros...but you're not restricted to using EnCase to perform analysis of the memory dumps produced by such tools. Using free tools, you can convert the .E0x files to a dd-style format, and then use other freely available tools to parse through the memory dumps.

Addendum: Got this from someone who ran kern.pl on a memory dump from XP SP3 recently...

File Description : NT Kernel & System
File Version : 5.1.2600.5512 (xpsp.080413-2111)
Internal Name : ntkrnlmp.exe
Original File Name :
Product Name : Microsoft(R) Windows(R) Operating System
Product Version : 5.1.2600.5512

Pretty sweet, eh?

If you're using winen.exe to collect the contents of RAM and you're also using EnCase, you might want to check out these EnScripts from TK_Lane that will pull process information from the .EOx files. I haven't tried them yet, but thanks, TK, for providing them!

Memory Collection and Analysis

As a follow-on to my previous post regarding OMFW, there have been some developments in the area of memory dumping and parsing (ie, collection and analysis) that have occurred over the past couple of months.

Lance Mueller posted on the new standalone memory dumping tool that is part of EnCase 6.11. Interesting tool as it apparently dumps the contents of physical memory from Windows (Windows 2000 through Vista) to an EnCase .E0x file format, for inclusion in a case. According to the documentation, there's functionality to extract that memory dump from the .E0x file format to something usable by HBGary's Responder product. Note: Initial testing indicates that FTK Imager will successfully convert the resulting .E0x files to a dd-style format for use with other tools.

Jesse Kornblum referred mdd to me. This one looks promising...captures memory from Windows versions through Vista and 2008. Jesse posted some clarifications about this tool on his blog. As it stands, this appears to be the first free tool to dump RAM from Windows 2000 through 2008, inclusive, in a dd-style format. Note: Updated version 1.1 was released on 17 June.

So available tools for collecting the contents of physical memory are becoming more available. From an analysis standpoint, I really think that you want to keep your eyes on the guys over at Volatility Systems, though.

Addendum: win32dd is available from Matthieu Suiche. I just found out about this so I haven't had an opportunity to try it...but I am looking forward to adding it to the list of tools to test!

Andreas blogs on the new tools...great stuff, very comprehensive view of where this all stands at the moment.

More Free Tools

To continue adding to the list of free tools (earlier posts here and here), here are a couple of gems I found recently...

NetworkMiner - a free network forensic analysis tool that takes analysis of network traffic captures to another level. Very cool tool...I love how WireShark lets you reassemble streams, but NetworkMiner lets you do a bit more, and it's Windows-based. Don't have any packet captures available to try it with? Check out the HoneyNet Project's SotM #27.

Thanks goes to Claus for pointing these out...

Stinger and MVC...these are NOT full-bore AV applications, but rather free tools meant to target specific malware. Use these on a live system, or mount the acquired image as a live file system (as opposed to booting the image...) and scan the files.

OpenFilesView - Neat little tool to see which files are open on a system; GUI based but comes with command line options, making it a great tool for use in IR batch files. Say you've got a suspected intrusion and you need to know if sensitive data (pursuant to PCI, HIPAA, etc.) is being siphoned off of the system...well, grab process information w/ tools like tlist.exe and correlate that information to files opened on the system by process...

MUICacheView - The NirSoft site says, "Each time that you start using a new application, Windows operating system automatically extract the application name from the version resource of the exe file, and stores it for using it later, in Registry key known as the 'MuiCache'." This is one of those things I've looked into, and I'm not able to find what the OS would use this for...but hey, who am I to complain about it, right?

By the way, RegRipper has a plugin for this key, which means that you can parse the contents of this key by either extracting the hive from an image, or by firing up F-Response. ;-)

Addendum: Claus posted some of his own bloggy goodness about Evidence Collector, and from that post I learned about USBHistory, a nice little tool that extracts historical information about USB devices connected to a live system. The author even gives a shout out to ol' watashe-wa and his book! Very cool!

Free Analysis

What??!? "Free" (as in 'beer') analysis? A bit ago, I blogged about Forensic Analysis on the Cheap, and I wanted to revisit that topic, particularly to mention a couple of tools I've run across since then...

Event Logs
In an earlier post, I mentioned some tools you could use to perform Event Log analysis. I still like the functionality in EvtUI (although I may be seen as biased because I wrote it), but if tools like this scare you, there are other options available. For example, Event Log Explorer is a nice little little app, and you can obtain a free license for its use. In direct mode, it works just like EvtUI, accessing the event records directly within a .evt file extracted from an acquired image.

Registry Analysis
I have to say that I'm really partial to RegRipper and its associated CLI utility, rip.exe. A couple of minor tweaks, as well as some new plugins, both of which were recently added, make this an immensely useful (not to mention unique) tool.

When looking for things I may want/need to add as plugins to RegRipper, my favorite Registry Viewer to use is MiTeC's RFV. I can go through the hive file and look at things, and fire rip.exe off against it without having to unload the hive or anything like that. RFV is a great Registry Viewer that facilitates the development of plugins.

File Carving
I've mentioned scalpel before as a tool for file carving...XaberSoft provides a GUI interface for setting up the scalpel config file

Another useful tool for file carving is PhotoRec. Even though its intended for extracting image files, I'm sure that there are a number of folks out there interested in doing just that...

Other Tools
Shadow Explorer - I haven't had an opportunity to try this tool yet, but I'm told that it's great for recovering files using Vista's Volume Shadow Copy Service. If you can boot an acquired image using LiveView, and log into the running image, you may be able to get some useful information or recover some files using this tool.

Registry Analysis - What Is It??

That's right...what is this thing we call "Registry analysis"? When someone performs "Registry analysis", what are they doing?

Okay...raise your hand if, for you, Registry analysis consists of looking for strings (using strings, or BinText, or your favorite tool), or maybe using grep() to do regex searches for IP addresses, email addresses, or something else.

Great, thanks. You can put your hands down.

Now, raise your hand if when performing Registry analysis, you open the hive files you're interested in with one of the popular Registry viewers (EnCase, FTK, ProDiscover, or even good ol' RegEdit), and "look around for anything interesting". Keep it up there if you use some sort of checklist or spreadsheet of Registry keys that may be of interest for your case or exam.

Okay...great. Go ahead and put your hands down.

So, what's wrong with either of these methodologies? Cumbersome? Inefficient? In some cases, ineffective? Ever wonder what you're missing? How about...A LOT?

The fact of the matter is, I really believe that Registry analysis isn't being performed today nearly as much as it should because it isn't "easy". I mean, sure, you've got this file that contains all this data, all this potential "evidence" (depending upon the audience, of course), but you don't know (a) how to get it, and maybe even (b) how to interpret it. After all, Registry viewers don't give you what you need, do they? They just present the data as is...it's up to you, the investigator or analyst to make heads or tails of it.

What if you just want to get the most recent document accessed...not just by the user, but via various applications, such as RealPlayer, maybe an image viewer, Excel, Adobe Reader, or even just by one of the common dialogs? If you're just looking for documents accessed, there are a LOT of places to look in the Registry...and using a checklist can take a long time. Also, due to encoding used by various vendors, regular ASCII/Unicode string searches won't work. So what if your "checklist" could be run against the Registry hive file itself?

What about those times when you have to correlate between multiple Registry keys, such as when you're trying to find out about those installed BHOs, or trying to determine when a USB thumb drive was last plugged into the system? How cumbersome is that?

How would you like to rip through your Registry analysis, getting just what you need, presented in the way you need it, or at least a way that's usable? Forget spreadsheets and checklists...how about plugins (stuff like Nessus and Metasploit use plugins, right?) that reach out and get what you want? How about...in order to update this tool, plugins just need to be dropped into a directory, and they're ready to use? How about it this all came with a GUI and a nice "FindAllEvidence" button?

What if you could also get timestamped data (ie, most recently accessed documents, UserAssist entries, etc.) so that you could import it into a format such as Excel, or even XML (for use with Simile TimeLine)?

Know what's really cool about the timestamped data? In order for it to be placed in the user's Registry hive file (NTUSER.DAT), the user account needs to be logged into the system. Sounds pretty simple, doesn't it? Hit most public lists, though, and you'll see questions such as, "how do I tell when a user was logged on if auditing of logon events isn't recorded in the Security Event Log?" (I'm paraphrasing, of course). Well, in most cases, when someone logs on, they do something...right? Look at all of the user activity that is recorded (I say 'recorded" because in many ways, the Registry is a log file, of sorts) in the user's hive file...and then correlate that to other activity (Internet browser history, etc.) that may be available.

Sound pretty cool? How about flippin' sweet?!?

The fact is, there's "lookin' at" the Registry, and then there's doing real Registry analysis and getting the data you need.

Addendum
Some might be wondering, "What is it about Registry analysis that's so hot? After all, I get all of the information/evidence I need from the file system." Well, I can only speak to those things that I've determined through Registry analysis...logon history, files accessed, files NOT accessed, applications that had been installed, run, and then uninstalled, etc. There is a great deal of information...much of it historical, much of it associated in some way with a time stamp...right there in the Registry.

Addendum, 1 Apr
Okay, this isn't a joke...but I added three plugins to the RegRipper last night. One for the Uninstall key in the Software hive (all entries sorted based on the key LastWrite times), as well as one for the USBStor key, and another for the DeviceClasses keys...both in the System hive.

Adding a plugin for the Protected Storage System Provider is going to be problematic until I get some info how to decrypt the data in the "Item Data" values.

Event Log Analysis

In keeping with the Getting Started posts, I wanted to include something that may be of interest with regards to finding corroborating artifacts when performing computer forensic analysis.

Many times, when performing CF analysis, we end up trying to find out when a particular user may have logged into a system, or into a Windows domain. There may be other artifacts, as well, that may lead us to the Windows Event Log (right now, I'm just talking about the Windows 2000, XP, and 2003 Event Logs). There are a number of different ways to go about this, using the commercial tools such as EnCase and ProDiscover, but sometimes the analyst may want to extract the .evt files from the acquired image and parse them. In such instances, the Windows API (used by the Event Viewer and a number of other tools) may report that the .evt file is "corrupted".

This has happened enough to others that I don't even bother any longer, and instead resort to tools such as EvtUI, a GUI-enabled Perl script based on the Evt2Xls Perl script that I wrote to parse .evt files on a binary basis, by-passing the MS API and producing something a bit more usable. EvtUI runs against an .evt file and parses out all of the event records into an Excel binary-compatible spreadsheet. The Time_Generated field of the event record structure is formated so that it can be used to sort on in the spreadsheet. EvtUI also produces a report file, which gives the analyst an overview of the .evt records based on the frequency of the various sources and event IDs. I found this particular functionality useful enough that I pulled it out into its own tool (I call it "evtrpt") and added a frequency count for event types (Info, Warning, Error, Success, and Failure). The report file also gives you the date ranges of all of the event records.

Another thing that EvtUI lets the analyst do is enter exceptions. I've seen instances with really large .evt files (when combined with an extremely verbose audit configuration) where .evt file will have more than 65,535 records...and this is the limit of entries for Excel. So, the analyst can run EvtUI once, and then check the report...if there are more than 65,535 records, she can choose event IDs to enter as exceptions and then re-run EvtUI.

Now, once you've gotten this far, the question then becomes, how do you analyze the data you've got? Well, what you look for depends not only on your case, but what's being audited (which you can see very easily by parsing the PolAdtEv value from the Security Registry hive file. This is only a start, though...I suggest that anyone who does or wants to do Event Log analysis check out the following sites:

EventID.net (indispensable and well worth the $24/yr subscription)
Eric Fitzgeralds' blog
Rob "Van" Hensing's Blog
Windows 2000 Security Event Descriptions (pt 1, 2)

Tips
There was an intrusion investigation where the intruder was suspected of having created an account (done in many cases in order to maintain persistence) within the domain. Auditing for logon events was not enabled, but auditing for account management events was...and I was able to quickly find an event ID 624 record showing the creation of the suspicious

Other Resources
EventLogRecord structure
Windows Event Log Reference (Vista, 2008)
GrokEVT (Python-based)
ScreenClean

When First Responders Attack!!

It still happens...an "event" or "incident" occurs within an organization, and the initial response from the folks on-site (most often, the organization's IT staff) obliterates some or all of the "evidence" of the event. Consultants are called to determine "how they got in", "how far they got" into the infrastructure, and "what data was taken", and as such, are unable to completely answer those questions (if at all) due to what happened in the first hours (or in some cases, days) after the incident was discovered.

Check out Ignorance wrecking evidence, from AdelaideNow in Australia. It's an excellent read from the perspective of law enforcement, but a good deal of what's said applies across the board.

One of the things that consultants see very often is a disparity between what first responders say they did during an initial interview, and what the analyst sees during an examination. Very often, the consultant is told that the first responders took the system offline, but didn't do anything else. However, analysis of the image shows that installing and running anti-virus and -spyware tools, deleting files, and even restoring files from backup all happened. A great deal of this can be seen once the approximate timeline of the incident is determined...and very often, you'll see an administrator login, install or delete/remove stuff, etc., and then say that they didn't do anything.

Why would this matter? Let's take a look...

Many analysts still rely on traditional examination techniques, focusing on file MAC times, etc. So an admin logs into a system and runs an AV or anti-spyware scan (or both...or just 'pokes around'...something that happens a LOT more than I care to think about...), so now all of the file access times on the system have been modified, and perhaps some files have been deleted. Anyone remember this article on anti-forensics that appeared in CIO Magazine? Why worry about that stuff, when there is more activity of this nature occurring due to either the operating system itself, or due to regular, day-to-day IT network ops?

So what's the solution? Education and training, starting with senior management. They have to make it important. After all, they're the ones that tell IT that systems have to stay up, right? If senior management were really aware of how many times (and how easily) their organization got punked or p0wned by some 15 yr old kid, then maybe they'd put some serious thought and effort into protecting their organization, their IT assets, and more importantly, the (re: YOUR) data that they store and process.

Getting started, or forensic analysis on the cheap

Quite often, I'll see posts or receive emails from folks asking about how to get started in the computer forensic analysis field. What most folks don't realize is that "getting into" this field really isn't so much about the classes you took at a college or the fact that you have a copy of EnCase. What it's about is how well you know your stuff, what you're capable of doing, and if you're capable of learning new stuff.

For example, who would you want to hire or work with...someone who only knows how to use one tool (for example, EnCase), or someone who can explain how EnCase does what it does (such as file signature analysis) and can come up with solutions for the problems and challenges that we all run into?

What I've decided to do is compile a list of free (as in "beer") resources that can be used by schools and individuals to develop labs, training exercises, etc., for the purposes of providing an educational background in the field of computer forensic analysis. With nothing more than a laptop and an Internet connection, anyone interested in computer forensics analysis can learn quite a lot without ever spending any $.

Imaging
FTK Imager 2.5.3 (and Lite 2.5.1)
George M. Garner, Jr's FAU
dcfldd - Wiki
dc3dd

Image/File Integrity Verification
MD5Deep

Images/Analysis Challenges
Lance's Forensic Practicals (#1 and #2) (no EnCase? Use FTK Imager to convert the .E0x files to dd format)
NIST Hacking Case
DFTT Tool Testing Images
HoneyNet Project Challenges
VMWare Appliances (FTK Imager will allow you to add these - most of which are *nix-based - as evidence items and create dd-format images)

Analysis Applications
TSK 2.51 (as of 10 Feb 2008...includes Windows versions of the tools, but not the Autopsy Forensic Browser - see the Wiki for how to use the tools)
NOTE: DFLabs is developing PTK, an alternative Sleuthkit interface, and they are reportedly working on a full Windows version, as well!
ProDiscover 4.9 Basic Edition
PyFlag

Mounting/Booting Images
VDK & VDKWin
LiveView (ProDiscover Basic will allow you to create the necessary .vmdk file for a dd-format image)
VMPlayer

Analysis Tools
Perl ('nuff said!!) - my answer for everything, it seems ;-)

File Analysis
MiTec Registry File Viewer - import Registry hive files
TextPad
Rifiuti - INFO2 file parser
BinText - like strings, but better
Windows File Analyzer

File Carving
Scalpel

Browser History
WebHistorian

Archive Utilities
Universal Extractor
jZip
PeaZip

AV and Related Tools

Miss Identify - identify Win32 PE files (different from an AV scan)
GriSoft AVG Free Edition anti-virus

Avira AntiVir PersonalEdition anti-virus
McAfee Stinger - standalone tool to scan for specific malware
ThreatFire (requires live system, best when used w/ AV)
GMER Rootkit Detection (requires live system)

Packet Capture and Analysis
PacketMon
WireShark

Other Tools
According to Claus at the GSD blog , Mozilla uses SQLite databases to store information, so if you're doing browser analysis, you may want to take a look at SQLite DB Browser, or SQLiteSpy. If you want to create your own databases in SQLite, check out SQLite Administrator. So, you can use these tools not only for analysis of the Mozilla files, but also with creating your own databases for use with other tools (ie, Perl).

Please keep in mind that this is just a list...and not an exhaustive one...of technical resources that are available. There are many, many other tools available.

Also, all of the technical tools and techniques are for naught if you (a) cannot follow a process, and (b) cannot document what you do.

Enter Sandman

You're probably wondering, "Since when did Metallica have anything to do with Windows forensics?"

My answer to that is...since ALWAYS!

Okay...enough of that. The Sandman I'm referring to isn't the one from the Metallica song. Rather this one has to do with the Windows hibernation file (get it? "sleep". "Sandman". get it? no...you don't...). Evidently Nicholas and Mattheiu has been working on a C library for reading/writing the Windows hibernation file. This sounds really cool, and it looks as if they're going to include Python bindings, as well as a couple of sample apps, one of which will reportedly convert a hibernation file into a dd-style memory dump. Very cool. Keep in mind, however, that a hibernation file doesn't contain the current contents of memory, but rather the contents of memory from when the file was created.

Sandman looks like a good tool to have in your kit, and I can't wait to try it out.

Who you gonna call?

Remember that old tag line from the '80's? It's right up there with "where's the beef!" However, my question is directed more toward forensic analysis, including anything collected during live response.

Where do you go for thoughts, input or validation regarding your live response process? Do you just grab a copy of Helix and run the WFT tools? Or are you concerned about doing that blindly (believe me, there are folks out there who aren't...), and want some kind of validation? (I'm not saying that WFT and toolkits like are bad...in fact, that's not the case at all. What I am saying is that running the tools without an understanding of what they're doing is a bad thing.)

What about analysis of an image? Do you ever reach out and ask someone for insight into your analysis, just to see if you've got all of your bases covered? If so, where do you go? Is it a tight group of folks you know, and you only contact them via email, or do you reach out to a listserv like CFID, or go on lists like ForensicFocus?

Another good example is the Linux Documentation Project and the list of HowTo documents. These are great sources of information...albeit not specific to forensic analysis...and something I've used myself.

NIST provides Special Publications in PDF format, and Security Horizon is distributed in PDF. CyberSpeak is a podcast. IronGeek posts videos, mostly due to hacking. I included a couple of desktop video captures on the DVD with my book, showing how to use some of the tools.

While agree that we don't need yet another resource to pile up on our desks and go unread, I do wonder at times why there isn't something out there specific to forensic analysis.

Forensic Analysis

Often (well, often enough) we run into instances where it becomes evident that someone has an unrealistic expectation of what answers forensic analysis can provide.

I know that right now, most of you are thinking, "dude...no way!" But I say, truly, it is so. There's even a term for it...it's called the CSI Effect. There are even articles written about it (here, and here).

Let's look at an example of what I mean. Our hero, the forensic analyst and incident responder Dude Diligence gets a call from a company, and the caller says that they've been "hacked" ("hacked" is the new "smurfed", by the way...a verb with many nuances and flavors...). Dude gets on site to find that even before he was called, a considerable amount of remediation was going on...systems were being accessed and "cleaned" (another one of those verbs with many nuances and flavors...) by administrators, with no real focus as to who was doing what, when, or why?

I'm sure that by now, some of you who are consultants like our hero are now weeping into your beers, sobbing, "dude..." under your breath...but our story continues.

Dude does the best he can to get the story of what happened, and what systems were affected. In the end, he acquires images of about half a dozen systems and returned to the Dude Lab to do analysis. Before leaving, however, he made sure that he had a solid understanding of what questions needed to be answered for the customer...specifically, was this a targeted attack, and was sensitive data (could be credit card numbers, could be PII, PHI, etc.) compromised.

To make a long story short, ultimately what Dude finds is that...he can't find anything. Systems had not been configured for any sort of viable logging (the system, as well as applications), and what logs that were there had been removed from the system. Systems had been scanned with AV applications, etc., etc. Traces of the intruder's activity (if there was one) had been completely obliterated by the actions of those who "responded" to the incident. Even if Dude had determined that sensitive information was, in fact, on the system, he isn't able to provide a definitive response to the question of, does that information now, as a result of the intrusion/compromise, exist somewhere it shouldn't? Was it exposed?

Even under the best of circumstances, there are just some questions that forensic analysis cannot answer. One question that comes up time and time again, particularly in some of the online forensic forums, is, from an imaged system, can you tell what files were copied off of the system? Dude has found artifacts of files being uploaded to web-based email systems such as GMail, and found other artifacts, but what computer forensic artifacts are there if someone opens a Word or PDF document on their screen and copies information out of it onto a piece of paper, using a pen? How about if someone connects a removable storage device to the system and copies the files off onto to that device? Sure, there are artifacts of the device being connected to the system (particularly on Windows systems), but without actually imaging and analyzing that removable storage device, how would Dude determine what files were copied from the system to the device?

I've talked about alternative analysis techniques before, and the solutions I'm looking toward include, for example, how you may be able to show names of files that someone viewed, and possibly the dates, even if the user deleted and overwrote the files themselves, or viewed them from removable media, etc. There are lots of ways to get additional information through analysis of the Registry, Event Logs, and even of the contents of RAM captured from the system...but there are just some questions that computer forensics can not answer.

That being said, how does our hero Dude Diligence go about his dude-ly analysis? Well, to begin with, Dude is part-sysadmin. This means that he understands, or knows that he needs to understand, the interrelation between the different components of a system...be that the interrelation between the external router, firewall, and the compromised system within the network infrastructure, or the interrelation between the network, the apparently compromised host (i.e., the operating system), and the applications running on the host.

When it comes to analyzing intrusions, Dude doesn't have to be a pen-tester or "ethical hacker"...although it may help. Instead, Dude needs to shift his focus a bit and not so much concentrate on breaking into or compromising a system, but instead concentrate "around" it...what artifacts are left, and where, by various actions, such as binding a reverse shell to the system through the buffer overflow of an application or service? For example, when someone logs into a system (over the network via NetBIOS or ssh or some other application, or at the console), where would Dude expect to see artifacts? What does it mean to Dude if the artifacts are there? What if they're not there?

Remember Harlan's Corollary to Jesse's First Law of Computer Forensics?

This leads us back to the first statement in this post...there are some actions for which the artifacts are not available to forensic analysts like Dude when he's performing a post-mortem analysis, and there are some questions that simply cannot be answered by that analysis. There are some questions that can be answered, if Dude pursues the appropriate areas in his analysis...

Windows Memory Analysis

It's been a while since I've blogged on memory analysis, I know. This is in part due to my work schedule, but it also has a bit to do with how things have apparently cooled off in this area...there just doesn't seem to be the flurry of activity that there was in the past...

However, I could be wrong on that. I had received an email from someone telling me that certain tools mentioned in my book were not available (of those mentioned...nc.exe, BinText, and pmdump.exe, only BinText seems to be no longer available via the FoundStone site), so I began looking around to see if this was, in fact, the case. While looking for pmdump.exe, I noticed that Arne had released a tool called memimager.exe recently, which allows you to dump the contents of RAM using the NtSystemDebugControl API. I downloaded memimager.exe and ran it on my XP SP2 system, and then ran lsproc.pl (a modified version of my lsproc.pl for Windows 2000 systems) against it and found:

0 0 Idle
408 2860 cmd.exe
2860 3052 memimager.exe
408 3608 firefox.exe
408 120 aim6.exe
408 3576 realsched.exe
120 192 aolsoftware.exe(x)
1144 3904 svchost.exe
408 2768 hqtray.exe
408 1744 WLTRAY.EXE
408 2696 stsystra.exe
244 408 explorer.exe

Look familiar? Sure it does, albeit the above is only an extract of the output. Memimager.exe appears to work very similar to the older version of George M. Garner, Jr's dd.exe (the one that accessed the PhysicalMemory object), particularly where areas of memory that could not be read were filled with 0's. I haven't tried memimager on a Windows 2003 (no SPs) system yet. However, it is important to note that Nigilant32 from Agile Risk Management is the only other freely available tool that I'm aware of that will allow you to dump the contents of PhysicalMemory from pre-Win2K3SP1 systems...it's included with Helix, but if you're a consultant thinking about using it, be sure to read the license agreement. If you're running Nigilant32 from the Helix CD, the AgileRM license agreement applies.

I also wanted to followup and see what AAron's been up to over at Volatile Systems...his Volatility Framework is extremely promising! From there, I went to check out his blog, and saw a couple of interesting posts and links. AAron is definitely one to watch in this area of study, and he's coming out with some really innovative tools.

One of the links on AAron's blog went to something called "Push the Red Button"...this apparently isn't the same RedButton from MWC, Inc. (the RedButton GUI is visible in fig 2-5 on page 50 of my first book...you can download your own copy of the "old skool" RedButton to play with), but is very interesting. One blogpost that caught my eye had to do with carving Registry hive files from memory dumps. I've looked at this recently, albeit from a different perspective...I've written code to locate Registry keys, values, and Event Log records in memory dumps. The code is very alpha at this point, but what I've found appears fairly promising. Running such code across an entire memory dump doesn't provide a great deal of context for your data, so I would strongly suggest first extracting the contents of process memory (perhaps using lspm.pl, found on the DVD with my book), or using a tool such as pmdump.exe to extract the process memory itself during incident response activities. Other tools of note for more general file carving include Scalpel and Foremost.

So...more than anything else, it looks like it's getting to be a good time to update processes and tools. I mentioned an upcoming speaking engagement earlier, and I'm sure that there will be other opportunities to speak on Windows memory analysis in the future.

Pimp my...Registry analysis

There are some great tools out there for viewing the Registry in an acquired image. EnCase has this, as does ProDiscover (I tend to prefer ProDiscover's ability to parse and display the Registry...) and AccessData's Registry Viewer. Other tools have similar abilities, as well. But you know what? Most times, I don't want to view the Registry. Nope. Most times, I don't care about 90% of what's there. That's why I wrote most of the tools available on the DVD that ships with my book, and why I continue to write other, similar tools.

For example, if I want to get an idea of the user's activity on a system, one of the first places I go is to the SAM hive, and see if the user had a local account on the system. From there, I go to the user's hive file (NTUSER.DAT) located in their profile, and start pulling out specific bits of information...parsing the UserAssist keys, etc...anything that shows not only the user's activities on the system, but also a timeline of that activity. Thanks to folks like Didier Stevens, we all have a greater understanding of the contents of the UserAssist keys.

Now, the same sort of thing applies to the entire system. For example, one of the tools I wrote allows me to type in a single command, and I'll know all of the USB removable storage devices that had been attached to the system, and when they were last attached. Note: this is system-wide information, but we now know how to tie that activity to a specific user.

On XP systems, we also have the Registry files in the Restore Points available for analysis. One great example of this is the LEO that wanted to know when a user had been moved from the Users to the Administrators group...by going back through the SAM hives maintained in the Restore Points, he was able to show approximately when that happened, and then tied that to other activity on the system, as well.

So...it's pretty clear that when it comes to Registry analysis, the RegEdit-style display of the Registry has limited usefulness. But it's also clear that there really isn't much of a commercial market for these kinds of tools. So what's the answer? Well, just like the folks who get their rides or cribs pimped out on TV, specialists bring a lot to the table. What needs to happen is greater communication of needs, and there are folks out there willing and able to fulfill that need.

Here's a good question to get discussion started...what's good, easy-to-use and easy-to-access format for a guideline of what's available in the Registry (and where)? I included an Excel spreadsheet with my book...does this work for folks? Is the "compiled HTML" (ie, *.chm) Windows Help format easier to use?

If you can't think of a good format, maybe the way to start is this...what information would you put into something like this, and how would you format or organize it?

Pimp my...forensics analysis

How often do you find yourself in the position where, when performing forensic analysis, you end up either not having the tools you need (ie, the tools you do have don't show you what you need, or don't provide you with useful output)? Many of the tools we use provide basic functionality, but there are very few tools that go beyond that, and are capable of providing what we need over a large number of cases (or in some instances, even examination to examination). This leads to one of the major challenges (IMHO) of the forensic community...having the right tool for the job. Oddly enough, there just isn't a great market for tools that do very specific things like parse binary files, extract data from the Registry, etc. The lack of such tools is very likely due to the volume of work (i.e., case load) that needs to be done, and to a lack of training...commercial GUI tools with buttons to push seem to be preferred over open-source command line tools, but only if the need is actually recognized. Do we always tell someone when we need something specific, or do we just put our heads down, push through on the investigation using the tools and skill sets that we have at hand, and never address the issue because of our work load?

With your forensic-analysis-tool-of-choice (FTK, EnCase, ProDiscover, etc.), many times you may still be left with the thought, "...that data isn't in a format I can easily understand or use...". Know what I mean? Ever been there? I'm sure you have...extract that Event Log file from an image and load it up into Event Viewer on your analysis system, only to be confronted with an error message telling you that the Event Log is "corrupted". What do you do? Boot the image with LiveView (version 0.6 is available, by the way) and log into it to view the Event Log? Got the password?

The answer to this dilemma is to take a page from Xzibit's book and "pimp my forensics analysis". That's right, we're going to customize or "trick it out" our systems with the tools and stuff you need to do the job.

One way to get started on this is to take a look at my book [WARNING: Shameless self-promotion approaching...], Windows Forensic Analysis; specifically at some of the tools that ship on the accompanying DVD. All of the tools were written in Perl, but all but a few have been "compiled" into standalone EXEs so that you don't have to have Perl installed to run them, or know anything about Perl -- in fact, based on the emails I have received since the book was released in May 2007, the real limiting factor appears to be nothing more than a lack of familiarity with running command line (CLI) tools (re: over-dependence on pushing buttons). The tools were developed out of my own needs, and my hope is that as folks read the book, they too will recognize the value in parsing the Event Log files, Registry, etc., as well as the value of the tools provided.

Another resource is the upcoming Perl Scripting for Forensic Investigation and Security, to be published in the near future by Syngress/Elsevier.

What do these two resources provide? In a nutshell, customized and customizable tools. While a number of tools exist that will let you view the Registry in the familiar (via RegEdit) tree-style format, how many of those tools will translate arbitrary binary data stored in the Registry values? How many will do correlation, not only between multiple keys within a hive, but across hives, as well?

How many of the tools will allow you to parse the contents of a Windows 2000, XP, or 2003 Event Log file into an Excel spreadsheet, in a format that is easily sorted and searched? Or report on various event record statistics?

How many of these tools provide the basis for growth and customization, in order to meet the needs of a future investigation? Some tools do...they provide base functionality, and allow the user to extend that functionality through scripting languages. Some are easier to learn than others, and some are more functional that others. But even these can be limiting sometimes.

The data is there, folks...what slows us down sometimes is either (a) not knowing that the data is there (and that a resource is a source of valuable data or evidence), and (b) not knowing how to get at that data and present it in a usable and understandable manner. Overcoming this is as simple as identifying what you need, and then reaching out to the Xzibits and Les Stroud's of the forensic community to get the job done. Rest assured, you're not the only one looking for that functionality...

Registry Analysis

You've probably noticed a huge gap between posts...sorry about that. Contrary to popular belief, I don't just sit around all day writing books. ;-) In addition to actually working, I like to think about ways to make my job easier, and to make the final product of my analysis better. Like many, I've known for sometime that considerable, valuable data exists in the Registry...there's a quite a bit there, whether you're looking for evidence of devices attached to the system, or of user activity. One of the things I've noticed is that there are a good number of tools available that allow you to do Registry data extraction...that is, pull data from the Registry, presenting the data found in a key or value. AccessData has their Registry Viewer, tools such as EnCase and ProDiscover allow you to visualize the Registry data...however, all of these are just tools, and each has their own strength and weakness.

One of the issues that confronts us today is knowing what we're looking at or looking for. Having a tool present data to us is nice, but if we don't know how that data is populated, then what good is the tool when some one-off condition is encountered? If the analyst does not understand how the artifact in question is created or modified, then what happens when the data that he or she expects to see is not present? Remember Jesse's First Law of Computer Forensics and my own subsequent corollary?

Why is this important? Well, for one, there's been a great deal of discussion about antiforensics lately, starting with a couple of articles in CIO and CSO magazines. "Antiforensics" and "counterforensics" (thanks to Richard for definitions) are not new concepts at all...the use of such activities has been around for quite some time. However, systems are becoming more and more complex, and at the same time, feature-rich. One of the benefits of Windows XP, for example, is that the feature-rich nature of the operating system goes some lengths in offsetting the inherent antiforensic features of the operating system.

So...let's try to come full circle...Registry analysis comes into play in assisting the investigator in determining what happened, and in many cases, when. Registry analysis can provide key or corroborating data. No tool out there will provide everything an investigator needs...it's up to the investigator to understand what's needed (ie, which Registry keys pertain to a particular P2P client, or which show the files most recently accessed with an image viewing utility?) and then understand how to get it. There are tools out there that do not have pretty GUIs and buttons you can push that will provide you with that information.

More on (the) UserAssist keys

Didier Stevens has continued some of his excellent work regarding the UserAssist keys in the Registry. This morning, he posted an entry that explains part of the value names that appear when you decode (ie, un-ROT-13) the names. He has added the capability of providing an explanation to his UserAssist tool.

When you decode the value names from beneath the UserAssist\{GUID}\Count keys, you see that the value names begin with "UEME_" and include names like "RUNPIDL" and "RUNCPL", to name just a few. Since research into these Registry entries began, no one has really known or explored what these refer to...until now. Didier has done an excellent (say "excellent" the way Mr. Burns...more data on Wikipedia...does from "The Simpons", while tenting your fingers...) job of digging into what they mean, as well as providing that explanation via his tool.

If you get a chance, please be sure to thank Didier for his work, and if you see him at a conference, buy him a beer!

Addendum, 5 Sept: Rich over at ForensicZone.com has an interesting web page posted about extracting UserAssist key value names from memory dumps. This is a very interesting move on Rich's part...I've been looking at memory dumps and finding the "magic numbers" for Registry keys and values, but I have yet (due to time constraints) to go as far as writing code to pull out the key/value structures. The interesting thing about this (I think...being the complete nerd that I am) is that if we dump the contents of physical memory and then are capable of parsing out images used by each process as well as the memory used by each process, we can then (potentially) find Registry keys and values that we can associate with a specific process, but have yet to be written to disk! In addition, we know from the Registry key structure that the keys (albeit not the values) have a timestamp associated with them, increasing their evidentary value. Great catch, Rich! I hope you and Didier keep up the great work you've been doing!

Addendum, 7 Sept: Wow, when things get rolling, it's amazing! Didier and I have exchanged a couple of emails discussing various aspects of the UserAssist keys and some of the more esoteric settings that are out there, and according to some, have actually been used! Didier's a veritable fountain of energy and enthusiasm when it comes to researching this kind of thing, so keep an eye on his blog for more good things!

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.

Thoughts on RAM acquisition

As a follow-on to the tool testing posts, I wanted to throw something else out there...specifically, I'll start with a comment I received, which said, in part:

Tool criteria include[sic] whether the data the tool has acquired actually existed.

This is a slightly different view of RAM acquisition (or "memory dumping") than I've seen before...perhaps the most common question/concern is more along the lines of, does exculpatory evidence get overwritten?

One of the issues here is that unlike a post-mortem acquisition of a hard drive (ie, the traditional "hook the drive up to a write-blocker, etc."), when acquiring or dumping RAM, one cannot use the same method and obtain the same results...reproduceability is an issue. Because you're acquiring the contents of physical memory from a running system, at any given point in time, something will be changing; processes process, threads execute, network connections time out, etc. So, similar to the live acquisition of a hard drive, you're going to have differences (remember, one of the aspects of cryptographic hash algorithms such as MD5 is that flipping a single bit will produce a different hash). I would suggest that the approach we should take to this is to accept it and document it.

That being said, what are some of the questions that we can anticipate addressing, and how would/should we answer them? I'll take a stab at a couple of basic questions (and responses), but I'd really like to see what others have to say:

1. Did you acquire this data using an accepted, validated process?

In order to respond to this question, we need to develop a process, in such a way as to validate it, and get it "accepted". Don't ask me by whom at this point...that's something we'll need to work on.

2. Did this process overwrite evidence, exculpatory or otherwise?

I really think that determining this is part of the validation process. In order to best answer this question, we have to look at the process that is used...are we using third-party software to do this, or are we using some other method? How does that method or process affect or impact the system we're working with?

3. Was this process subverted by malware running on the system?

This needs to be part of the validation process, as well, but also part of our analysis of the data we retrieved.

4. Did you add anything to this data once you had collected it, or modify it in any way?

This particular question is not so much a technical question (though we do have to determine if our tools impact the output file in anyway) as it is a question for the responder or examiner.

As you can see, there's still a great deal of work to be done. However, please don't think for an instant that I'm suggesting that acquiring the contents of physical memory is the be-all and end-all of forensic analysis. It's a tool...a tool that when properly used can produce some very valuable results.

Restore Point Analysis

Others have posted bits and pieces regarding System Restore Point analysis (Stephen Bunting's site has some great info), and I've even blogged on this topic before, but I wanted to add a bit more information and a tidbit or two I've run across. This will go a bit beyond what's in my book, but I do want to say that the content in my book is not invalidated in any way.

First off, you can use some of the tools on the DVD accompanying my book in either live response or during post-mortem analysis to collect information from the Restore Points. I've recently updated the code to the SysRestore.pl ProDiscover ProScript to make it more usable and flexible, given some situations I've seen recently.

Another interesting thing I've run across is that using an alternative method of analysis, such as mounting the acquired image as a read-only drive letter (using VDKWin or Mount Image Pro), can be more of a problem than a solution. Accessing the system this way can really be a boon to the examiner, as you can hit the system with an AV scanner (...or two...or three...) and save yourself a great deal of time trying to locate malware. However, the problem occurs due to the fact that the ACLs on the System Volume Information directory require System level access for that system, and even having System level access on your analysis system does not equate to System level access on the mounted image. So things tend not to work as well...files within the "protected" directories will not be scanned, and your alternative is to either perform your analysis within a forensic analysis application such as ProDiscover (using ProScripts), or export the entire directory structure out of the image, at which point, storage is then a consideration (I've seen systems with quite a number of Restore Points).

This is can be an issue because bad guys may try to hide stuff in these directories...read on...

Remember me mentioning the existence of web browsing history for the Default User? This indicates the use of the WinInet API (wget.exe, IE, etc.) by someone who accessed the system with System level privileges. This level of access would also allow that user to access the System Volume Information directory, where the Restore Points are maintained, and possibly put things there, such as executable image files, etc. It's unlikely that a restore point would be used for persistence (ie, point a Windows Service to an executable image within a restore point), as the restore points eventually get deleted or flushed out (see the fifo.log file). However, this would be an excellent place to put an installer or downloader file, and then the intruder could place the files that he wanted to be persistent in either the System Volume Information directory, or the "_restore*" directory.

So, besides looking for files that we know are in the Restore Points (ie, drivetable.txt, rp.log, Registry files), we should also consider looking for files that shouldn't be there, particularly if we find other artifacts that indicate a System-level intrusion.

Beyond this, Restore Points provide a wealth of historical information about the system. By parsing all of the rp.log files, we can develop a timeline of activity on the system that will give us an idea of what was done (system checkpoint, application install/uninstall, etc.) as well as provide us with that timeline...if the Restore Points are in sequence and the dates seem skewed, then we have an indication that someone may have fiddled with the system time. Using the drivetable.txt file, you can see what drives were attached to the system at the time that the Restore Point was created (by default, one is created every 24 hrs).

Beyond these files, we also have access to the Registry files that are backed up to the Restore Points. You can parse these to see if and when a user's privilege levels were modified (ie, added to the Administrator group), determine IP addresses and network settings for the system (parse the NetworkCards key from the Software file, then the Tcpip Services key from the System file), etc.

Analysis of the Registry files maintained in Restore Points is also useful in determining a timeline for certain Registry modifications that are difficult to pin down. For example, when a Registry value is added or modified, the key's LastWrite time is updated. What if one value is added, and one is modified...how do we determine which action caused the LastWrite time to be modified? Well, by using the historical data maintained in the Restore Points, we can look back and see that on this date, the modified value was there, but the added value wasn't...and then it appears in the next Restore Point. Not exact, but it does give us a timeline.

So...what interesting things have you found in Restore Points?

Links
Kelly's Korner (XP Restore Points)
MS Windows XP System Restore
System Restore WMI Classes