Computer Online Forensic Evidence Extractor (COFEE) is a software program developed by Microsoft for use by law enforcement. It was held closely by law enforcement for a period of time until it was revealed in the last year, and subsequently, several individuals released software intended to defeat the utility of COFEE. While a big deal has been made of the secrecy of this tool and other related matters, reasoned examination has been somewhat lacking in the open community, even though there have been validation studies undertaken of the tool. Thus this limited review of the situation is suited to this special end-of-year edition.
In this sense, COFEE is really no different from programs like ForensiX or older menu-based systems for running programs, except that it is wrapped in a particular methodology and implemented on a USB drive to be useful for working on "live systems". There are many "live" forensics tools that do similar, or in many cases, what appear to be more forensically sound and larger collections of, jobs of extracting data from systems as they operate.
Study 1 was undertaken under a US Department of Justice Federal grant. "This validation study was conducted to verify COFEE properly formats, wipes, and generates profile(s) to a thumb drive, including its ability to generate a report from collected data. This validation study was conducted to ensure that COFEE consistently completed all of its required actions." The study concludes that COFEE passed all of the tests it was given, and more specifically, that it "successfully generated a listed profile, a user created profile, formatted an attached device as FAT 32 and overwrote or wiped data existing in unallocated space on the device. COFEE successfully generated a detailed report of the results of the collected data from a specified profile. There were no unexpected anomalies found during testing." A list of 18 assertions were identified for testing, and one test environment was configured for the validation. These assertions largely portray the specifics summarized above, and tests included verification that formatting of the drive fails when inadequate space is present and gives a proper error notice. This study did not provide any useful details about performance of the other functions, and makes no particular assertions about tool use, alterations to the target system, or the correctness of results, other than the performance of specific actions by the interface program as identified therein.
Study 2 defines itself well; "COFEE's primary purpose is to create a thumb drive which contains a pre-determined set of applications which are set to run on a suspect's live machine. Upon connecting a COFEE generated thumb drive to a suspect's machine, the investigator executes runner.exe (a program located on the thumb drive) which, in turn, executes all of the programs specified by COFEE, and stores the data collected on the investigator's thumb drive. The programs placed on the generated thumb drives are identified by a "profile" loaded into COFEE. While any user can create their own profile, this validation study will focus only on the profiles created by NW3C: "NW3C - Volatile Data" and "NW3C - Incident Response." This validation study was conducted to ensure that when runner.exe is executed: all of the programs identified by the profile are executed, that the collected data is stored on the investigator's thumb drive, that no applications were run from the suspect's machine, and that no unacceptable writes were made to the suspect's machine. COFEE is currently only supported on the Microsoft Windows XP operating system. No other operating system was tested during this validation study."
The conclusions from this study were a bit over the top, as we will soon see, but for two graduate students, this represents a reasonably strong effort. They conclude "Testing conducted on Runner and the NW3C profiles verified that both the runner.exe application, as well as the selected programs, functioned as expected and are well within acceptable practices for data collection on a live system." ... "NW3C - Volatile Data Profile - There wereno writes to the suspect drive's file system using this profile. There were updates made to the Windows Registry on the suspect's machine, however none of the registry updates were of obvious forensic value." ... "NW3C - Incident Response Profile - This profile attempted to make five writes to the target computer's file system. Three of the writes were caused by the program handle.exe and were made to the file "PROCEXP100.sys." The reference to the file PROCEXP100.sys is hard-coded into handle.exe, a product of Sysinternals, and as such it is not possible to restrain handle.exe from writing to this file. However, this file is specifically written as part of the Sysinternals' toolset and is unlikely to be of any evidentiary interest. The other two attempted writes were made to network shares on the target computer, and were also unlikely to be of any evidentiary interest. There were also updates made to the Windows Registry on the suspect's machine, however none of the registry updates were of obvious forensic value."
This study used 3 different configurations of computers, and tested the following conditions:
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