Tuesday, October 21, 2014

Windows Event Logs

Dan recently tweeted:

Most complete forensics-focused Event Log write-ups?

I have no idea what that means.  I'm going to assume that what Dan's looking for is information regarding Event Logs records that have been found useful or valuable to forensic analysts, or potentially could be.

EVT vs EVTX
Windows XP is no longer supported by Microsoft, but there are still XP and 2003 systems out there, and as such, some of us are still going to need to know the difference between Event Logs (XP, 2003), and Windows Event Logs (Vista+).

Besides the binary differences in the records and Event Log files themselves, on XP/2003, there were three main Event Log files; System, Application, and Security.  On my Windows 7 system, a 'dir' of the winevt\Logs folder reports 143 files.  So, there is a LOT of information being recorded by default on a Windows 7 system; while not all of it may be useful to you, there is a great deal of information that can be extracted from the logs when used properly.

Wevtx.bat
When I released Windows Forensic Toolkit 4/e, one of the things included in the additional materials is a batch file, wevtx.bat.  What the batch file does is use LogParser to parse a directory full of .evtx files, and then parse those entries into TLN format for inclusion in a timeline.  The tool evtxparse.exe, used by the batch file, makes use of a mapping file (i.e., eventmap.txt) to map event source/ID pairs to an artifact category tag.  As such, when the entry in written to a timeline, records such as "Microsoft-Windows-Security-Auditing/4624" are prepended with an appropriate tag (i.e., "[Logon]"), based on the artifact category.

I really love this tool!  What I like about it is that it's easy to update (eventmap.txt is just a text file), I can add comments to it to show the source of the information I used to map an event record to something specific, and it acts as a fantastic little repository for all of my past experiences.  Not only is it a great repository, but it's incorporated right into the tools that I use on just about every engagement.

Records
Here are some of the event source/ID pairs that I've found to be useful during investigations, for such things as malware detection, determining the window of compromise, etc.  I'll say up front that these records are not 100% infallible, and may not have extremely high fidelity (some do, others don't...), but they've worked quite well for me at one time or another, so I'll share them here.

Microsoft-Windows-DNS-Client/1014 – DNS name resolution timeout; I've used this one more than once to help demonstrate that malware was on a system, even in the face of anti-forensics techniques (time stomping the malware files, deleting the malware files, etc.). It's not a 100%, infallible indicator, but it's worked for me more than once.  What has also helped is when this event record was seen; in a timeline, I could see that it occurred shortly after a user logged into a laptop, and before the user connected the system to a WAP.  This helped me narrow down the persistence mechanism for the malware.

Microsoft-Windows-Security-Auditing/4720 - user account created; because the bad guys do this from time to time.

McLogEvent/257 – McAfee malware detection - McAfee AV may detect malware behaviors (i.e., run from a Temp folder, etc.) without actually detecting the EXE itself.  This can be very valuable in helping you determine how malware got onto a system.  Also, the AV product may be configured to warn only, and take no action..so, correlate the event records (UTC) to the entries in the McAfee logs (local system time)

Microsoft-Windows-Windows Defender/3004 – Windows Defender malware detection

Service Control Manager/7045 – A service was installed on the system

Service Control Manager/7030 – A service is configured to interact with the desktop

Microsoft-Windows-TaskScheduler/106 - New Scheduled Task registration

Beyond individual event records (source/ID pairs), one of the aspects of the newer versions of Windows (in particular, Windows 7) is that there are a lot of events that are being recorded by default, across multiple Event Log files.  What I mean is that when some events occur, multiple event records are recorded, often across different Event Log files.  For example, when a user logs into a system at the console, there will be an event recorded in the Security Event Log, a couple in the Microsoft-Windows-TerminalServices-LocalSessionManager/Operational.evtx log, and a couple of events will also be recorded in the Microsoft-Windows-TaskScheduler/Operational.evtx log.  Alone, each of these individual events may get little attention from an analyst, but when placed together in a timeline, they leave an indelible mark indicating that a user logged into the system.

Now, what's really great about this is that some of the Event Logs "roll over" faster than others.  As such, some of the source/ID pairs that are part of an indicator cluster may have been expired from their respective Event Logs.  However, the remaining source/ID pairs in the cluster will still provide a very good indicator that that event in question took place.  This is particular useful for infrequent events, and I've used this information more than once to demonstrate repeated activity going back weeks and even months prior to what was thought to be the date of interest.

Anti-Forensics
Event auditing is one of those things that just happens in the background on Windows systems.  This is great, because sometimes Event Log records can help us determine if anti-forensics techniques have been employed.  For example, using Event Log records, you can determine if someone has changed the system time.

During an exam, I found that a system had been infected with malware that installed as a Windows service, and during the installation process, the .exe file had been time-stomped.  Fortunately, when the malicious service was installed, an event source/ID pair of "Service Control Manager/7045" was created, indicating that a new service had been installed on the system.  I was able to correlate that information with other sources (MFT, etc.) to better determine the correct time of when the malicious .exe was created on the system, and nail down the infection vector.

Carving
If you need to carve Windows Event Log records, for any reason...from unallocated space, memory, the pagefile, whatever...the tool to use is Willi Ballentin's EVTXtract. The "tool" is really a set of Python scripts that you run consecutively against the data in order to recover Windows Event Log records.  I've used these scripts a couple of times, and even had a fellow team member use them on an engagement and quite literally recover the "smoking gun".

When carving for deleted records on a Windows XP or 2003 system, I use a custom Perl script that I wrote that's based on some of the code I've released with my books.

Timelines
When all this is said and done, a blog post on just individual Windows Event Log records isn't really all that valuable.  Yes, I've created timelines from just a handful of *.evtx files, for use in triage, etc.  This has proved to be extremely valuable to me.

Resources
WindowsIR: Timeline Analysis
SANS Reading Room: Detecting Security Events Using Windows Workstation Event Logs
NSA: Spotting the Adversary with Windows Event Log Monitoring

Monday, October 20, 2014

Publishing DFIR Books

I recently received notification that Syngress is interesting in publishing a second edition of Windows Registry Forensics.  I submitted my proposed outline, the reviews of which were apparently favorable enough to warrant a second edition.

I've blogged before regarding writing DFIR books, and that effort seems to have fizzed a bit.  I wanted to take the opportunity to give another shot and see if I couldn't resurrect this topic, or a portion of it, just a bit.  So, the purpose of this blog post is two-fold: to set expectations of the upcoming edition, as well as offer those in the community who are interested to have input into the development (what goes in it) of the book.

Based on the reviews of my proposed outline, as well as some of the online reviews (Amazon, SecurityXploded, etc.), I wanted address a few of the comments I  tend to see more frequently than most, and then allow those who read this post to make their own comments.

From the SecurityXploded review:

It would have been better if author would have put up the approach or step by step procedure one should follow while analyzing live & offline system.

...and...

Putting things straight and then discussing relevant tools at each step will be more beneficial.

This is always an interesting statement to pursue, in part because I see it pretty often in things I've written (such as the HowTo blog posts from July 2013), as well as course materials and presentations I, and others, have put together.  As I'm sure others have done, I try to write something that is general enough to apply across multiple situations, and hope that the reader is able to extrapolate what I've written so it can be used in their specific situation.  My thinking...and it may be wrong...is that analysts must be able to take what they've learned from white papers, presentations, training courses, and other sources, and apply that information and knowledge to what they have available to them.  Not everything that an analyst encounters is going to fit neatly into a training course or whitepaper; there's always going to be some twist or variation, based on the goals of the examination, the data available, etc.  As such, analysts need to be able to build on core principles and basic knowledge to be able to meet the challenges before them.

For example, an analyst should be able to review the SANS checklist for analyzing USB devices on Windows 7, read this HowTo (Correlate an attached device to a user) and this HowTo (Determine user access to files), and be able to determine the files a user may have accessed from a thumb drive that had been attached to their system.  Part of this entails that there has to be some point at which a common, baseline level of knowledge must be assumed.  For example, do you assume that most folks know what the Registry is, or how to determine the CurrentControlSet from a System hive extracted from an acquired image?

This is why I advocate that analysts must share their experiences; no one of knows everything, but together, we can know more than any one of us.  None of us is going to have the same experiences as everyone else, but we can all learn from each other's experiences.

Another comment from the SecurityXploded blog post:

However if you are expecting to cover all those important registry locations then you will be disappointed and it is not feasible in one book. 

This is exactly right, and goes back to one of the core things I learned about writing DFIR books...you're not going to make everyone happy.  Someone's always going to be disappointed about what they didn't find in the book.  But you know what...that's okay.  It has to be...if someone tried to write a book that covered everything, that book would never be completed.

I've been working directly in the DFIR field for a little more than 14 years, and I will be the first to admit, I have not seen everything there is to see.  I've done DFIR in an internal, FTE position, as well as as a consultant.  For a bit more than three years, I did PCI response while at IBM ISS.  While my work has evolved over time, there is still a great deal that I haven't seen, and when I write books or blog posts, I most often base what I write about my own direct experiences.  Now and again, someone will share data with me, and I will learn a little something from their experiences.  I like to sprinkle those indirect experiences in, as well, because they broaden the reach of the material.

In WRF 2/e, I do plan to provide examples of analysis processes I've used, based on goals I've been given, as well as things that I've seen during analysis.  However, no one should expect to pick up this book (or any other DFIR book, for that matter) and find the answer to their specific issue or question.  This is particularly true if no effort is made to contact the author while the book was being written.

From the WRF 2/e outline reviews, as well as from other sources, I've seen this little gem:

You need to provide a chapter on Windows Phone 8.

Anyone remember this blog post?  There were two important take-aways from that blog post.  One was that RegRipper does work with the Windows Phone 8 Registry, and what's needed is sample data and input into what examiners find important, so that plugins can be written.  The second is that the hive files were provided to me...I do not own a Windows Phone 8, nor do I have access to these devices, through work or any other means.  Cindy Murphy did send me some hive files extracted from a Windows Phone 8, but that's one system and a very limited amount of data.  I can't write about what I don't know and didn't experience, and can't provide screen captures illustrating data that I do not have.  Would I like to write more about the Windows Phone 8, particularly the Registry?  Sure.  Without a doubt.  But without actual data, I can't really be expected to write much of anything, can I?

Okay, those are just a few of the comments/statements I've seen in reviews, and like I said, I only wanted to address those that I see regularly.  If you have any thoughts or comments about the content that should appear in WRF 2/e, I'd be glad to hear and consider them.  Thanks.

Monday, October 06, 2014

Stuff

IR
Here's a really good...no, I take that back...a great blog post by Sean Mason on "IR muscle memory".  Take the time to give it a read, it'll be worth it, for no other reason than because it's valuable advice.  Incident response cannot be something that you talk about once and never actually do; it needs to be part of muscle memory.  Can you detect an incident, and if so, how does your organization react?  Or, if you receive an external notification of a security incident, how does your organization respond?


A couple of quotes from the blog post that I found interesting were:

...say, “Containment” without having any understanding of what is involved...

Yes, sometimes a consultant (or CISSP) will say this, and sometimes, there is that lack of understanding of how this will affect the business.  This is why having IR built into the DNA of an organization is so important...understanding how the business will be affected by some response or containment procedure is critical.

There is also a modicum of patience and discipline required when it comes to containment, particularly when it comes to targeted threats.  If the necessary instrumentation is not in place to monitor the environment, then prematurely pulling the trigger on some containment procedures rather than taking the time to prepare and conduct the containment procedures in a near-simultaneous manner will likely cause the threat actors to react, changing what they do.  When dealing with these incidents, if someone on the response team decides, "...hey, I can make that change now, so I'll go ahead and take care of it..." can lead to a lot more work.

Another comment from the blog post:

...as a leader and a technologist, you always want everyone to know everything wing-to-wing, and while this can work great in a small organization the reality is that it doesn’t scale for a number of reasons in larger orgs. 

I agree wholeheartedly with this.  For larger teams in particular, it doesn't scale well for everyone to be an expert in everything, but it does work well to have designated pockets of deep expertise.

I know that I'll never be as good a malware reverse engineer as some of the folks I've had the honor of working with.  I can put a great deal of effort into becoming good at it, but that effort would be effort that I wouldn't be spending become better at DFIR analysis.  Also, I've found that an effective approach is to gather as much as I can about the malware...OS and version it's installed on, where it was found in the file system, persistence mechanism, any artifacts or indicators associated with the malware, etc.  I provide these to the RE analyst, and continue my analysis while they dig deep into the malware itself.  When the RE analyst finds something, they provide it back to me and I continue with my analysis.

A great example of this occurred a number of years ago.  I have found some malware that was used to steal banking credentials (NOT Zeus) and shared it with the RE analyst, providing a second file and the information/intel needed to run the malware.  The malware itself was obfuscated, and in return I got a mutex (I didn't have a memory dump, but I did have a hibernation file and the pagefile), the API used for off-system communications, and other valuable information.  With that, I was able to nail down the specific user affected, the initial infection vector, when the infection occurred, etc.

On smaller teams, you won't be able to have those silos, but on larger teams, in larger organizations, it helps to pockets of deep expertise, and someone you can reach to for further assistance.  This is particularly valuable in incidents, due to the ability to perform parallel analysis; rather than having one analyst who many not, say, analyze disk images on a regular basis try to wring as much information and intel out of an acquired image as they can while working an IR engagement, have that task run in parallel by someone with a deeper expertise.  You're likely to get the info you need (and more) in a much more timely manner, while not loosing any time or focus on the engagement itself.  On smaller teams, you're likely going to have a broader base of skill sets that aren't as deep as what you will find with individuals on larger teams.  Larger teams can take advantage of pockets of skill sets, and even geographic dispersion, to keep the flow of the incident response going.

The rest of Sean's blog post is equally interesting.  Sean goes on to provide his thoughts on people, process, and metrics, all with great insight.

To further Sean's thoughts, a great follow-on to his post is this article from WSJ; in particular, the following quote from that article:

“You are going to get hacked. The bad guy will get you. Whether you are viewed as a success by your board of directors is going to depend on your response.”

IR Fail?
Here's an interesting article from Kelly Jackson Higgins (DarkReading) that talks about Fortune 500 companies having IR teams, but many being pessimistic about their team's ability to handle a data breach.  From my perspective, it's good to see that more firms are moving to having a computer security incident response plan, or CSIRP, and that these companies are actually thinking about things like, "...we need a plan...", and "...how good is our IR team?"  Even if there is pessimism about the current team's effectiveness, at least there's thought going in that direction, and a realization and admission of the team's current state.  From my perspective, this isn't really so much of a failure as it is a success that we've come this far.

From the article:

So why are aren't Target, TJ Maxx, and others sharing their war stories to help the next potential victim?

Yeah, you're not going to.  Sharing is not a natural reaction within the DFIR community.  This doesn't mean that it doesn't happen...years ago, while working an IR with a client, I heard that there was a forum in the local area where IT folks from different organizations in the same vertical came together and discussed issues and solutions.  In fact, the DLP solution that my client had in place, which proved to be extremely valuable during the IR engagement, had been purchased as a result of engaging with others in their community.  My point is, sharing can be powerful, and sharing information or intel that helps the next guy when they're attacked doesn't necessarily give away 'secret sauce' or competitive advantage.

Having an IR plan in place isn't enough, either.

No, it's not.  You can't have a plan written by consultants sitting on a shelf...that's worse than not having a plan at all, because the organization will see that binder sitting on the shelf (literally or figuratively) and think that they've checked a box and have achieved some modicum of success.  A CSIRP needs to be organic to an organization (remember Sean's blog post?); it needs to be owned and practiced by the organization.  You can get assistance in writing it, reviewing it, and practicing the processes laid out in the CSIRP.  Having an outside consulting firm come in and run an IR exercise...anything from a table top (in the military, we called this a "tactical exercise without troops", or TEWT) exercise to a full-on IR engagement...is a fantastic idea.

Over the years, I've seen a wide variety of organizations as a consultant.  I've seen those that have been caught completely by surprise by a data breach, those that have IR plans but do not employ them, and I've seen those that have a practiced plan and want someone there to help guide them.  Invariably, those organizations that have been thinking seriously about the need for incident detection and response end up faring much better than others, in a variety of metrics, including the overall cost of the incident.

RegRipper
In a few short weeks, I will be presenting at OSDFCon, talking about some changes to RegRipper that I've had in the works.  I'll say right now that the changes I've been thinking about and working on are not ones that will significantly impact the use of the tool...so come on by and give it a listen.

OSDFCon and OMFW
I've attended and presented at OSDFCon before, and this is has always been a really great conference to attend.

Whether you're going to be at OSDFCon or not, I highly recommend that you consider attending the Open Memory Forensics Workshop, or OMFW 2014.  This is the premier conference on memory analysis, put on by the top minds in memory analysis, from the Volatility Foundation.

If you're attending OSDFCon, be sure to come see Mari DeGrazia's presentation!

RegRipper Tutorial
Speaking of RegRipper, this tutorial was posted recently regarding how to set up and use RegRipper...I have say, I have somewhat mixed feelings about it.  Part of me appreciates the interest in the tool, but

In the name of full disclosure, the author did contact me and ask me to review the article after it was complete.  I responded, but to be honest, at the time that the request came in, I didn't have the cycles to focus on reviewing the article, and I definitely didn't have the cycles to address everything that I read in the article.  So what you're seeing now is what I've worked on a few minutes at a time, here and there, since the article was published.  I'm not going to address everything in the article, because I simply don't have the time to do so, so what I opted to do was pull out just a couple of comments and address them here.

For example...

I have often heard RegRipper mentioned on forums and websites and how it was supposed to make examining event logs, registry files and other similar files a breeze. 

I'm not sure which forums or websites state this, but this is not the case at all.  RegRipper is named as it is because it's intended for use against the Windows Registry...and only the Registry.  It's not intended for use against any other files, in particular the Windows Event Logs.  Right after I first released RegRipper, I did receive a request to have it parse PST files, but that simply wasn't/isn't practical.

As I wrote earlier there is a huge community out there writing plugins for RegRipper.

First off, there is no mention of "a huge community" in the tutorial, up to that point.  Second, there is not a "huge community out there writing plugins".  Yes, some plugins have been submitted over time, and some folks have suggested modifications to plugins...but there is not a "huge community" by any means.  In fact, my understanding is that the vast majority of users simply download the tool and run the GUI...and that's it.  Asking users specifically, via email or in person, what they'd like to see done to make the tool more useful does not often lead to responses such as requests for new plugins.

I could continue with a lot of the different things I found to be amiss (such as in the Downloads section), but it is not my intent to deride this effort.  Again, I greatly appreciate the interest in the tool, and I wanted to address a couple of the comments because I felt that they were wide-spread misconceptions that should be addressed.  I'm not going to do a walk-through and correct everything I find...instead, I'll refer folks to the various blog posts I've written, as well as to Windows Registry Forensics.



Sunday, September 07, 2014

Windows Phone 8 and RegRipper

Last week, Cindy Murphy (@cindymurph) sent me some Registry hive files...from a Windows Phone 8.  This was pretty fascinating, and fortunate, because I'd never seen a Windows phone, and had no idea if it had a Registry.  Well, thanks to Cindy, I now know that it does!

Looking at the hive files was pretty fascinating.  The first thing I did was open one of the smaller hive files in UltraEdit, and I could clearly see that it followed the basic structure of a Registry hive file (see chapter 2 of Windows Registry Forensics).  Next, I opened one of the hives in a viewer, and saw that the hive file opened nicely; however, there were clearly differences in what I expected to see, with respect to a desktop or laptop running Windows.

Finally, I ran a couple of RegRipper plugins against the System hive that Cindy provided, in part because I saw that there were some keys with the same paths as the ones I generally see on Windows systems.  For example, the compname.pl and timezone.pl plugins worked just fine.  For the Software hive, the profilelist.pl plugin worked just fine, although there was only one profile listed.  Interestingly enough, the SAM hive had the correct structure and a root key, but no subkeys.

So, if there's a question as to whether or not RegRipper works when run against hive files from a Windows Phone 8, the answer is "yes", but with a caveat...you can't expect all of the plugins to work, simply because the current RegRipper plugins are intended to run against hives extracted from Windows computer systems.  I would like to be able to write plugins for the phone hives, but I won't be able to that until more data becomes available and more analysts can identify what it is they find important and of-interest in these hive files.

I'd like to send a thank you to Cindy for sharing the hive files and helping to expand my view into this data source a bit.





Thursday, September 04, 2014

What Does That Look Like, Pt II

In my last post, I talked about sharing what things "look like" on a system, and as something of a follow up to that post, this article was published on the Dell SecureWorks blog, illustrating indicators of the use of lateral movement via the 'at.exe' command.  I wanted to take a moment to provide some additional insight into that post, with a view towards potentially-available indicators that did not make it into the article, simply because I felt that they didn't fit with the focus of the article.

Terminology
Some definitions before moving on...I'm providing these as living, "working" definitions that can be tweaked and modified as we go along.  I know that going into this, there will be those who ask for definitions, as well as those who see the definitions and simply say, "no, that's not what that means"...and that's okay.  We have to start somewhere, right?

Artifact - an element of a data source.  A data source might be a Windows Event Log file, and an artifact would be a Windows Event Log record.

Indicator - an artifact, with some sort of context applied to it.  That context may vary, which means the value of the indicator may vary.  As I mentioned before, sharing indicators, even those we've seen before or those we believe others have already seen is very valuable, in that it allows us to increase the reliability of those indicators.

Some mathy stuff to help provide a description...

Indicator = artifact + context

TTPs - clusters of indicators that can be used to illustrate intruder or user actions

Like I said, these are working definitions that can be tweaked and modified, if necessary.  I do think that they are important to have, as it provides us with a common platform from which to launch discussion and discourse.  Too often, discussions get tangled and confused over terminology and definitions, such as the difference between a Registry key and value; the distinction may be subtle, even irrelevant to some, but to others, they speak to the clarity and precision of the discussion.

If you read through the SecureWorks article, you might think that there are some things missing, particularly from the perspective of the source system in the lateral movement.  The article states that the observed indicator of the lateral movement is an application prefetch file for at.exe, and that's pretty much the case.  The purpose of the article is to show those indicators that (a) are not often looked at, and (b) persist well beyond the removal of tools, etc.

It's clear that for this lateral movement to function properly, the file (or files) launched by the Scheduled Task need to be moved to the destination system before the task is registered.  For example, an executable file might be copied to the destination system using a command such as:

cmd.exe - copy rar.exe \\host\c$\windows\tool1.exe

The above command (which I've obfuscated, for obvious reasons) was found on a source system, in the pagefile.  Again, this was found on a source system involved in lateral movement.  This is just an example of what you might find.  Unlike the use of PSExec, the tool/executable being run needs to be available on the destination system before it can be launched via a Scheduled Task, and the use of the copy command, used in conjunction with compromised credentials, is one way to get the file on the destination system.

Now, let's assume that the tool used ("tool1.exe") is, in fact, a copy of rar.exe and is used to archive some files...you might find an at.exe command similar to the below in the pagefile, as well:

cmd.exe - at \\host 3:00am cmd /c
"c:\windows\tool1.exe a c:\windows\m.exe -m5  c:\windows\r.txt"

Again, this is just an example of what you might find...any actual commands used by the intruder would clearly vary based on what they wanted to achieve.

Something to consider with respect to the above command is the time parameter.  In the article, I provided some indicators to look for with respect to the Scheduled Task being registered, and with the use of the time parameter, you may see a time gap between when the task is registered, and when it's actually executed.  I saw one task that was run a full 30 minutes after it had been registered on the destination system.  This can have an effect on your timeline analysis, so be aware/wary of it.

When it's all said and done, the intruder may then delete files used or created using commands similar to the below:

del \\host\c$\windows\r.txt

What's interesting is that, of the above commands (run on the source system during lateral movement), only the one used to create the Scheduled Task (via at.exe) will result in an application prefetch file being created, as indicated in "Source Host" section of the article (NOTE: this will only occur on a system that is configured to create application prefetch files; by default, Windows server systems do NOT create application prefetch files).  Unless you have some instrumentation in place for monitoring process creation and command lines (Sysmon, Carbon Black, etc.), or if you're able to detect this activity and collect a memory sample from a system relatively quickly, you may miss the above indicators extracted from the pagefile.  Keep in mind, too, that the above commands are simply examples, and were found in the pagefile; as such, they have no time stamps associated with them, and cannot be tied directly to what was seen in the article.

Also, one of the things I've talked about at great length is how much what we see on a Windows system is controlled by values in the Registry; the above indicators would have been obviated if the system was configured such that the pagefile was cleared on shutdown, and the system was cleanly shut down prior to an image being acquired.

Finally, once again, the purpose of the article posted to the Dell SecureWorks blog was to illustrate those indicators that tend to persist over time.

Thursday, August 21, 2014

What does that "look like"?

We've heard this question a lot, haven't we?

I attended a conference about 2 1/2 years ago, and the agenda for that conference had about half a dozen or more presentations that contained "APT" in their title.  I attended several of them, and I have to say...I walked out of some of them.  However, hearing comments from other attendees, many folks felt exactly the same way; not only were they under-whelmed, but I heard several attendees express their disappointment with respect to the content of these presentations.  During one presentation, the speaker stated that the bad guys, "...move laterally."  One of the attendees asked, "what does that look like on systems?", and the speaker's response was to repeat his previous statement.  It was immediately clear that he had no idea...but then, neither did anyone else.

Corey has asked this question in his blog, and he's also done some great work demonstrating what various activities "look like" on systems, such as when systems are exploited using a particular vulnerability.

What I'm referring to in this post isn't (well, mostly...) something like "...look at this Registry key."  Rather, it's about clusters or groups of artifacts that are indicative of an action or event that occurred on a system.

Clustering
As we share and use artifacts, we can take a step back and look at where those artifacts exist on systems.  Then we begin to see that, depending upon the types of cases we're working, artifacts are clustered in relatively few data sources.  What this means is that on drives that are 500GB, 1TB, or larger, I'm really only interested in a few MB of actual data.  This means that during incident response activities, I can focus my attention on those data sources, and more quickly triage systems.  Rather than backing up a van full of hard drives and imaging 300 or more systems, I can quickly narrow down my approach to the few systems that truly need to be acquired and analyzed.

This also means a significant speed-up for digital analysis, as well.  I don't maintain tables of how long it takes to acquire different hard drives, but not long ago, I had one hard drive that took 9 hrs to acquire, and another that was 250GB that took 5 hrs to acquire.  Knowing the data sources that would provide the biggest bang for the buck, I could have retrieved those after I connected the hard drive to the write-blocker, but before I acquired the hard drive image.

Reliability
As we share and use artifacts, we begin to see things again and again.  This is a very good thing, because it shows us that the artifacts are reliable.

Like others, including Corey, I don't see sharing artifacts on any sort of scale.  Yes, there are sites such as forensicartifacts.com, but they don't appear to be heavily trafficked or used.  Also, I generally don't find the types of artifacts I'm looking for at those sites.  I've been achieving reliability, on my own, for various artifacts by using them across cases.  For example, I found one particular artifact that nailed down a particular variant of a lateral movement technique; once I completed my analysis of that system, I went back and searched the entire timeline I'd developed for that system, and found that that artifact was unique to the event I was interested in.  I've since been able to use that artifact to quickly search successive timelines, significantly speeding up my analysis process.  Not finding that artifact is equally important, as well, because (a) it tells me that I need to look for something else, and (b) in searching for it, I can show a client that I've done an extremely thorough job of analysis, and done it much quicker.

Oxidation
A great reason for sharing artifacts is the oxidation of those artifacts.  Okay, so what does this mean?

The type of artifacts I'm referring to are, for the most part, not single artifacts.  Rather, when I talk about what something "looks like" on a system, I'm generally referring to a number of artifacts (Windows Event Log records, Registry keys/values, etc.) clustered "near" each other in a timeline.  How "near" they are...ranging from within the same second to perhaps a couple of seconds apart...can vary.  So, let's say that you're doing some testing and replicating a particular activity, and you immediately "freeze" your test system and find six artifacts that, when clustered near each other, are indicative of the action you took.

How many times as incident responders and digital forensic analysts do we get access to a system immediately after the initial intrusion occurred?  What's more likely to happen is that the initial response occurs hours, days, or even weeks after in the initial incident, and is the result of an alert or a victim notification.  Given the passage of time, these artifact clusters tend to oxidize due to the passage of time, as the system continues to run, and to be used.  For example, if a system becomes infected by a browser drive-by and IE is used in the infrastructure, some artifacts of the drive-by may be oxidized simply due to the normal IE cache maintenance mechanism.  Logs with fixed file sizes roll over, the operating system may delete files based on some sort of timing mechanism, etc.  All of this assumes, of course, that someone hasn't done something to purposely remove those artifacts.

Someone may share a cluster of six artifacts that indicate a particular event.  As others incorporate those artifacts into their analysis, the reliability of that cluster grows.  Then someone analyzes a system on which two of those six artifacts have oxidized, and shares their findings, we can see how reliable the remaining four artifacts can be.

I specifically chose to use the term "oxidize", because the term "expire" or "expired" seem to imply that the lifetime of the artifact had passed.  Sometimes, specific artifacts may not be part of a cluster, due to specific actions taken by the intruder.  For example, we've all seen files be deleted, time stomped, and other actions taken that force artifacts to be removed, rather than allowing them to timeout.

Format
At the moment, there are many questions with respect to sharing artifacts; one is the format.  What format is most useful to get examiners to incorporate those artifacts into their analysis?  Because, after all...what's the point of sharing these artifacts if others aren't going to incorporate them into their analysis processes?

During July, 2013, I posted a number of articles to this blog that I referred to as "HowTos"...they were narratives that described what to look for on systems, given various analysis goals.  Unfortunately, the response (in general) to those articles was the Internet equivalent of "cool story, bro."

A great indicator that I've used comes from pg 553 of The Art of Memory Forensics.  The indicator I'm referring to is pretty easy to pick out on that page...I've highlighted it in green in my book.  The authors shared it with us, and I found it valuable enough to write a RegRipper plugin so that I can incorporate that information directly into my own timelines for analysis...and yes, I have found this artifact extremely accurate and reliable, and as such, very valuable.  Having incorporated this indicator into my work, I began to see other artifacts clustered "around" the indicator in my timelines.  I also found that the indicator maintained it's reliability when some of those other artifacts were oxidized due to the passage of time; in one instance, the *.pf file was deleted due to how Windows XP manages the contents of that folder.

Final Thoughts
A good deal of the indicators that I'm referring to can be abstracted to more general cases.  What I mean is, an artifact cluster that is indicative of targeted threat (or "APT") can be abstracted and used to determine if a system was infected with commodity malware.  Other artifact clusters can similarly be extrapolated to more general cases...it's really more about how reliable the artifacts in the cluster are, than anything else.

Wednesday, July 30, 2014

Book Review: "The Art of Memory Forensics"

I recently received a copy of The Art of Memory Forensics (thanks, Jamie!!), with a request that I write a review of the book.  Being a somewhat outspoken proponent of constructive and thoughtful feedback within the DFIR community, I agreed.

This is the seminal resource/tome on memory analysis, brought to you by THE top minds in the field.  The book covers Windows, Linux, and Mac memory analysis, and as such must be part of every DFIR analyst's reading and reference list.  The book is 858 pages (not including the ToC, Introduction, and index), and is quite literally packed with valuable information.

Some context is necessary...I'm writing this review as someone who has used Volatility for some time, albeit not to it's fullest possible extent.  I'm more of an incident responder, and not so much a malware reverse engineer; I tend to work with some really good malware RE folks and usually go to them for the deeper stuff.  I've converted hibernation files and found some pretty interesting artifacts within the resulting raw memory (my case notes are rife with some of these artifacts), and I've reached to Jamie Levy on several occasions for support.  In addition, I recently completed the five-day Volatility training course.

Also, I spend most of my time working on Windows systems; as such, I cannot offer a great deal of value, nor insight, when it comes to reviewing the information that this book contains on Linux and Mac memory. However, I have worked with some of the folks who provided material for these sections, and I've seen them present at the Open Memory Forensics Workshop (OMFW), and to say that these folks are competent is a gross understatement.

That being said, this book is the most comprehensive reference that covers the topic of memory analysis, from start to finish, available.  The authors begin the book by providing a detailed description of system architecture, as it pertains to memory, discussing address translation and paging (among other topics) before progressing into data structures.  This ground-up approach provides the foundational knowledge that's really required for a complete understanding of memory analysis.  The book then proceeds with a complete walk-through of the Volatility Framework itself, covering topics such as plugins, basic and advanced usage, etc.  There is even a chapter that covers just memory acquisition, addressing tools, tool usage, and hive extraction (using the TSK tools) to assist in profile identification.  All of this information is covered prior to addressing actual memory analysis, so that by the time a reader gets to chapter 5, they should have some understanding of memory structure and how to acquire memory.

Something pointed out in chapter 4 (Memory Acquisition) is worth repeating...that memory acquisition via software is a "topic of heated debate".  While the authors do provide a comprehensive list of software tools that can be used to acquire memory, they also state that the list is not to be viewed as an evaluation, nor should the reader consider the fact that a tool is on the list as an endorsement of that tool.  As such, YMMV based on personal experience...

Throughout the book, the authors bring their incredible wealth of experience to bear in this book, as well.  After all, who better to write a book such as this than the folks who developed the Volatility Framework as a means to meet their own needs in memory analysis, while working on what are arguably the most technologically complex cases seen.  The section on Windows memory forensics covers 14 chapters, and interspersed throughout those chapters are examples of how memory analysis can be used to assist in a wide range of analysis.  Each section starts with an "objectives" section that outlines what the reader can expect to understand once they've completed the section, and many sections provide IRL (or near-IRL) examples of how to use Volatility to support the analysis in question.  As such, the authors are not just providing a "...use this plugin...", as much as they're also providing examples of what the output of the plugin means, and how it pertains to the investigation or analysis in question.

At this point, I've had my copy of the book for a few days, and I've had a ruler and highlighter on hand since I first cracked the spine.  The formatting of the book is such that I've already started adding my own notes to the margins, based on my own exams.  I've found it valuable to go back to case notes and write notes in the margins of the book, adding context from my own exams to what the author's have provided.  This simply increases the value to the book as a reference resource.  In addition, the book is rife with caveats, concerns, and tidbits...such as the section on Timestomping Registry Keys, and what intruders have done that modify the LastWrite time of the Policy\Secrets key in the Security hive.  There's even an entire section on timelining!

If you have an interest in memory analysis, this is THE MUST-HAVE resource!  To say that if you or anyone on your team is analyzing Windows systems and doesn't have this book on your shelf is wrong, is wholly incorrect.  Do NOT keep this book on a shelf...keep it on your desk, and open!  Within the first two weeks of this book arriving into your hands, it should have a well-worn spine, and dirty finger prints and stains on the pages!  If you have a team of analysts, purchase multiple copies and engage the analysts in discussions.  If one of your analysts receives a laptop system for analysis and the report does not include information regarding the analysis of the hibernation file, I would recommend asking them why - they may have a perfectly legitimate reason for not analyzing this file, but if you had read even just a few chapters of this book, you'd understand why memory analysis is too important to ignore.