Linkz for Tools

Wednesday, August 15, 2012 Posted by Corey Harrell
In this Linkz edition I’m mentioning write-ups discussing tools. A range of items are covered from the registry to malware to jump lists to timelines to processes.

RegRipper Updates

Harlan has been pretty busy updating RegRipper. First RegRipper version 2.5 was released then there were some changes to where Regripper is hosted along with some nice new plugins. Check out Harlan’s posts for all the information. I wanted to touch on a few of the updates though. The updates to Regripper included the ability to run directly against volume shadow copies and parse big data. The significance to parsing big data is apparent in his new plugin that parses the shim cache which is an awesome artifact (link up next). Another excellent addition to RegRipper is the shellbags plugin since it parses Windows 7 shell bags. Harlan’s latest post Shellbags Analysis highlights the forensic significance to shell bags and why one may want to look at the information they contain. I think these are awesome updates; now one tool can be used to parse registry data when it used to take three separate tools. Not to be left out the community has been submitting some plugins as well. To only mention a few Hal Pomeranz provided some plugins to extract Putty and WinSCP information and Elizabeth Schweinsberg added plugins to parse different Run keys. The latest RR plugin download has the plugins submitted by the community. Seriously, if you use RegRipper and haven’t checked out any of these updates then what are you waiting for?

Shim Cache

Mandiant’s post Leveraging the Application Compatibility Cache in Forensic Investigations explained the forensic significance of the Windows Application Compatibility Database. Furthermore, Mandiant released the Shim Cache Parser script to parse the appcompatcache registry key in the System hive. The post, script, and information Mandiant released speaks for itself. Plain and simple, it rocks. So far the shim cache has been valuable for me on fraud and malware cases. Case in point, at times when working malware cases programs execute on a system but the usual program execution artifacts (such as prefetch files) doesn’t show it. I see this pretty frequently with downloaders which are programs whose sole purpose is to download and execute additional malware. The usual program execution artifacts may not show the program running but the shim cache was a gold mine. Not only did it reflect the downloaders executing but the information provided more context to the activity I saw in my timelines. What’s even cooler than the shim cache? Well there are now two different programs that can extract the information from the registry.

Searching Virus Total

Continuing on with the malware topic, Didier Stevens released a virustotal-search program. The program will search for VirusTotal reports using a file’s hash (MD5, SHA1, SHA256) and produces a csv file showing the results. One cool thing about the program is it only performs hash searches against Virustotal so a file never gets uploaded. I see numerous uses for this program since it accepts a file containing a list of hashes as input. One way I’m going to start using virustotal-search is for malware detection. One area I tend to look at for malware and exploits are temporary folders in user profiles. It wouldn’t take too much to search those folders looking for any files with an executable, Java archive, or PDF file signatures. Then for each file found perform a search on the file’s hash to determine if VirusTotal detects it as malicious. Best of all, this entire process could be automated and run in the background as you perform your examination.

Malware Strings

Rounding out my linkz about malware related tools comes from the Hexacorn blog. Adam released Hexdrive version 0.3. In Adam’s own words the concept behind Hexdrive is to “extract a subset of all strings from a given file/sample in order to reduce time needed for finding ‘juicy’ stuff – meaning: any string that can be associated with a) malware b) any other category”. Using Hexdrive makes reviewing strings so much easier. You can think of it as applying a filter across the strings to initially see only the relevant ones typically associated with malware. Then afterwards all of the strings can be viewed using something like Bintext or Strings. It’s a nice data reduction technique and is now my first go to tool when looking at strings in a suspected malicious file.

Log2timeline Updates

Log2timeline has been updated a few times since I last spoke about it on the blog. The latest release is version 0.64. There have been quite a few updates ranging from small bug fixes to new input modules to changing the output of some modules. To see all the updates check out the changelog.

Most of the time when I see people reference log2timeline they are creating timelines using either the default module lists (such as winxp) or log2timeline-sift. Everyone does things differently and there is nothing wrong with these approaches. Personally, both approaches doesn’t exactly meet my needs. The majority of the systems I encounter have numerous user profiles stored on them which mean these profiles contain files with timestamps log2timeline extracts. Running a default module list (such as winxp) or log2timeline-sift against the all the user profiles is an issue for me. Why should I include timeline data for all user accounts instead of the one or two user profiles of interest? Why include the internet history for 10 accounts when I only care about one user? Not only does it take additional time for timeline creation but it results in a lot more data then what I need thus slowing down my analysis. I take a different approach; an approach that better meets my needs for all types of cases.

I narrow my focus down to specific user accounts. I either confirm who the person of interest is which tells me what user profiles to examine. Or I check the user profile timestamps to determine which ones to focus on. What exactly does this have to do with log2timeline? The answer lies in the –e switch since it can exclude files or folders. The –e switch can be used to exclude all user profiles I don’t care about. There’s 10 user profiles and I only care about 2 profiles but I only want to run one log2timeline command. No problem if you use the –e switch. To illustrate let’s say I’m looking at the Internet Explorer history on a Windows 7 system with five user profiles: corey, sam, mike, sally b, and alice. I only need to see the browser history for the corey user account but I don’t want to run multiple log2timeline commands. This is where the –e switch comes into play as shown below: -z local -f iehistory -r -e Users\\sam,Users\\mike,"Users\\sally b",Users\\alice,"Users\\All Users" -w timeline.csv C:\

The exclusion switch eliminates anything containing the text used in the switch. I could have used sam instead of Users\\sam but then I might miss some important files such as anything containing the text “sam”. Using a file path limits the amount of data that is skipped but will still eliminate any file or folder that falls within those user profiles (actually anything falling under the C root directory containing the text Users\username). Notice the use of the double back slashes (\\) and the quotes; for the command to work properly this is needed. What’s the command’s end result? The Internet history from every profile stored in the Users folder except for the sam, mike, sally b, alice, and all user profiles is parsed. I know most people don’t run multiple log2timeline commands when generating timelines since they only pick one of the default modules list. Taking the same scenario where I’m only interested in the corey user account on a Windows 7 box check out the command below. This will parse every Windows 7 artifact except for the excluded user profiles (note the command will impact the filesystem metadata for those accounts if the MFT is parsed as well). -z local -f win7 -r -e Users\\sam,Users\\mike,"Users\\sally b",Users\\alice,"Users\\All Users" -w timeline.csv C:\

The end result is a timeline focused only on the user accounts of interest. Personally, I don't use the default module lists in log2timeline but I wanted to show different ways to use the -e switch.

Time and Date Website

Daylight savings time does not occur on the same day each year. One day I was looking around the Internet for a website showing the exact dates when previous daylight savings time changes occurred. I came across the website. The site has some cool things. There’s a converter to change the date and time from one timezone to another. There’s a timezone map showing where the various timezones are located. A portion of the site even explains what Daylight Savings Time is. The icing on the cake is the world clock where you can select any timezone to get additional information including the historical dates of when Daylight Savings Time occurred. Here is the historical information for the Eastern Timezone for the time period from the year 2000 to 2009. This will be a useful site when you need to make sure that your timestamps are properly taken into consideration Daylight Savings Time.

Jump Lists

The day has finally arrived; over the past few months I’ve been seeing more Windows 7 systems than Windows XP. This means the artifacts available in the Windows 7 operating system are playing a greater role in my cases. One of those artifacts is jump lists and Woanware released a new version of Jumplister which parses them. This new version has the ability to parse out the DestList data and performs a lookup on the AppID.

Process, Process, Process

Despite all the awesome tools people release they won’t be much use if there isn’t a process in place to use them. I could buy the best saws and hammers but they would be worthless to me building a house since I don’t know the process one uses to build a house. I see digital forensics tools in the same light and in hindsight maybe I should have put these links first. Lance is back blogging over at ForensicKB and he posted a draft to the Forensic Process Lifecycle. The lifecycle covers the entire digital forensic process from the Preparation steps to triage to imaging to analysis to report writing. I think this one is a gem and it’s great to see others outlining a digital forensic process to follow. If you live under a rock then this next link may be a surprise but a few months back SANS released their Digital Forensics and Incident Response poster. The poster has two sides; one outlines various Windows artifacts while the other outlines the SANs process to find malware. The artifact side is great and makes a good reference hanging on the wall. However, I really liked seeing and reading about the SANs malware detection process since I’ve never had the opportunity to attend their courses or read their training materials. I highly recommend for anyone to get a copy of the poster (paper and/or electronic versions). I’ve been slacking updating my methodology page but over the weekend I updated a few things. The most obvious is adding links to my relevant blog posts. The other change and maybe less obvious is I moved around some examination steps so they are more efficient for malware cases. The steps reflect the fastest process I’ve found yet to not only find malware on a system but to determine how malware got there. Just an FYI, the methodology is not only limited to malware cases since I use the same process for fraud and acceptable use policy violations.
  1. Good stuff. On the Shim Parser stuff, I eneded playing with this information after stumbling onto it after reading the Mandiant Breach report which had references to that key. It's a wealth of imformation and actually made me recall a few malware variants that were zeroing it out, I just didn't realize what they were doing at the time. On thing to not is that this information is not written to the key until after a reboot, but is memory resident in winlogon.exe until then. pretty's like a memory resident prefetch.

  2. Time and time again the shim cache has come through to me. It even can in handy today looking at a system that was "cleaned". Thanks for the info about the registry key not updating until after a reboot. I've been meaning to do testing and your comment made me realize it needs to be sooner rather than later. The Application Compatibility has more artifacts than just the shim cache. One of which is something I'm looking into and if useful will be mentioned on my blog.

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