So you've just completed your forensic examination and found that forensic gem or smoking gun in your case, so how do you proceed? Depending on where you fall as a forensicator (e.g., law enforcement, intelligence, criminal defense work, incident response, e-discovery) you will have to report your findings. Foremost, find out what type of work product you are going to be required to produce to the client, attorney, etc. This will be your guide for completing your report. While the report writing part of the digital forensic examination process is not as fun as the forensic analysis, it is a very important link in the chain as Dave Hull summed it up here in a tweet.
As digital forensic examiners/analysts, we must report and present our findings on a very technical discipline in a simplistic manner. That may be to a supervisor, client, attorney, etc. or even to a judge and jury who will read and interpret your report after it has been cross-examined. Are you prepared to explain your findings? When the case goes to trial and you are called upon to testify a year or more in the future will you be able to remember the case based simply from the details you included in your report?
You've probably found yourself at some point diving right into an exam, completing your forensic analysis and theoretically going back to the beginning of the exam when it comes time to begin your report because the lack of note-taking during the forensic examination. A solid forensic examination requires detailed notes along the way. What exactly are good notes? Taking screenshots, bookmarking evidence via your forensic application of choice (EnCase, FTK, X-Ways Forensics, etc.), using built-in logging/reporting options within your forensic tool, highlighting and exporting data items into .csv or .txt files, or even using a digital audio recorder vs. handwritten notes when necessary. Jim O'Gorman provides some good tips for taking good notes during a digital forensic examination. As Jim discusses, there is no wrong way to take notes, nor a standard. Every examiner approaches the note-taking process differently, the important piece is to document, document, document. The more notes you take, the easier your report will be to prepare and finalize. Speaking of notes, Joe Garcia has provided an excellent review and walk-through of using CaseNotes during digital forensics.
Now we take our detailed notes to complete the forensic report to tell the story of what the presence or absence of the digital artifact indicates, regardless, if it is inculpatory or exculpatory in nature. Your report may include something similar or a slightly different flavor to: an overview/case summary, forensic acquisition & exam preparation, findings and report (i.e., forensic analysis), and a conclusion.
Overview/Case Summary
Example:
- On today's date, John Doe contacted my office in regards to imaging a stolen laptop computer running Windows® XP Professional that had been recovered. Doe is requesting a forensic examination to see what company documents may have been stolen by the suspect(s) and is requesting a full forensic examination and report for possible criminal charges & civil litigation.
This section will vary in length. You will include any relevant information regarding what led to you as the forensic examiner/analyst becoming involved with the digital evidence. You may be just receiving the forensic image and someone else conducted the forensic acquisition and this is a good place to document that as this will correlate with your chain of custody information that you immediately started once you came into contact with the digital evidence. Remember, this is an overview and a summary of how the case was initialized and where you as the examiner/analyst became involved.
Forensic Acquisition & Exam Preparation
Example:
- On today's date I began the forensic acquisition/imaging process of the stolen laptop. Prior to imaging the stolen laptop, I photographed the laptop, documenting any identifiers (e.g., make, model, serial #), unique markings, visible damage, etc. while maintaining chain of custody.
- Using a sterile storage media (examination medium) that had been previously forensically wiped and verified by this examiner (MD5 hash value: ed6be165b631918f3cca01eccad378dd) using ABC tool version 1.0. The MD5 hash value for the examination medium yielded the same MD5 hash value as previous forensic wipes to sterilize this media.
- At this point, I removed the hard drive from the stolen laptop and connected it to my hardware write-blocker, which is running the most recent firmware and has been verified by this examiner. After connecting the hardware write blocker to the suspect hard drive, I connected the hardware write blocker via USB 2.0 to my forensic examination machine to begin the forensic imaging process?
- Etc, etc.
This section is very important, as you must detail your interaction with the digital evidence and the steps taken to preserve and forensically acquire the evidence. Any additional steps that you take (e.g. forensically wiping storage/examination media, etc.) should be notated in this section of your report. Remember, this section of your report is usually where you as the examiner/analyst came into contact with the digital evidence and thoroughly documenting what you have done is very important to the integrity of the digital evidence and your chain of custody.
Examiner's Tip: You should have a digital camera in your forensic toolkit. Take a picture of the evidence and document each step of the forensic acquisition and preparation process. Regardless, if you include the picture in your report or as an exhibit, this picture is a perfect field note for you as the examiner to reference when completing your report.
- You will also need to include that you verified your forensic image and notate the hash values (e.g., MD5, SHA-1).
- You will also need to briefly describe the process you used when making a working copy from the forensic image of the original evidence.
Findings and Report (Forensic Analysis)
Example:
- After completing the forensic acquisition of the stolen laptop I began analyzing the forensic image of the stolen laptop with Forensic Tool
- I used the following tools for forensic analysis, which are licensed to this examiner:
- Guidance® Software's EnCase® 6.17
- SANS Investigative Forensic Toolkit (SIFT) Version 2.0
- Internet Evidence Finder v3.3
- RegRipper by Harlan Carvey
- Microsoft® Excel 2007
- A review of the Internet history using Internet Evidence Finder, the following data was recovered from sector 117004, which shows a Facebook email between John Doe and Jane Doe. Further analysis shows that a John Doe logged into his Google Mail account. See screenshots below:
John Doe logging into Google Mail account.
John Doe logging into Google Mail account.
This is the most detailed section of your investigation. You will include all artifacts that you find during your analysis relating to the case.
Examiner's Tip: A very good practice when you are including your evidence into your report is to include hyperlinks within your report to link to pictures, documents, etc. Make sure you test and validate that the hyperlinks work properly so when your report is being reviewed, the reader can navigate easily to the evidence that you are including in your report.
Conclusion
In this section, you are basing your conclusion off the forensic evidence. Remember, the goal of the forensic examination is to report the facts, regardless if the evidence is inculpatory or exculpatory in nature. A successful forensic examination is one that is very thorough and one in which you "leave no stone unturned". In the scenario that I provided using a recovered stolen laptop, what else might you include besides e-mail and browser forensics in your analysis to put the suspect in possession and at the keyboard of the stolen laptop? What about registry analysis to see what IP addresses the machine connected to in the SYSTEM hive: \CurrentControlSet\Services\{Adapter}\Parameters\Tcpip key? Where else would you look and what would you look for?
This post is for informational purposes and a guide for the new forensic examiner. Your report will vary in length and format. A forensic examination report could be just a few pages in length or maybe 20+ pages, depending on the type of case, department/ company expectations, and policy & procedure.
Mr. Brad Garnett, CCE, GCFA is a computer forensic examiner and law enforcement officer. You can follow Brad on Twitter @bgarnett17 and his blog at www.computerforensicsource.com