Encase Forensics
Here are some basic steps for carrying out Computer Forensics using Encase:
1. Assume we need to do Forensic Analysis of a compromised/crime-suspected Computer
2. For a computer there are several components for which Computer Forensics can be carried out, such as Disk Drive (DD), RAM, USB storage device, etc. Here, we will focus on Disk Drive only
3. Data Acquisition: The first step a Computer Forensics investigation is to acquisition of the evidence. That is: to obtain a bit-wise replica of the disk drive without compromising its integrity. To ensure integrity of the disk drive, all write-operation must be blocked while imaging. For this, combination of acquisition/imaging software such as EnCase or FTK Imager along with a hardware based Write-Blocker bridge such as Tableau Bridge (http://www.tableau.com/) can be used.
Common Forensics Acquired File Formats are:
a) DD /RAW (“Disk Dump”)
b) AFF (Advanced Forensic Format)
c) E01 (EnCase )
To acquire image with EnCase and Tableau Bridge:
1. Shutdown the crime-suspected computer. Disconnect the target disk drive from and connect to EnCase host system through Tableau Bridge in Read-Only mode.
2. Open EnCase and create a new Case. Click Add Device and navigate to the target disk drive through ‘Local Drives’ icon. Acquire image of the disk drive by right clicking and choosing ‘Acquire’
3. The image is stored in EnCase format chunks: E01, E02, E03,...etc.
Note: EnCase for DOS Utility (DOS based) and EnCase LinEn Utility (Linux based) are available in form of bootable disks. Crime-suspected computer can be shutdown and rebooted from these bootable disks. These bootable disks allow acquisition of data with software based write-blocker.
4. Data Verification: At the completion of the acquisition process, EnCase calculates an MD5 hash. The hash value is written into the evidence file. When we add evidence file to a case, the CRC value is automatically verified and the hash value for the evidence data is recomputed. It helps to ensure that evidence file has not changed since it was acquired.
Note: To recompute the hash value of the image, right click on the image, and select Hash.
If you have been provided with a Raw Image (example: DD format Disk Image created through FTK Imager) and its hash value or without hash value, then you can compute hash value through md5deep.exe utility from www. md5deep.sourceforge.net for future references:
md5deep -e filename-dd.001
5. Now, Open EnCase and create your Case
6. If you have got Raw Image, then go to File menu and select “Add Raw Image” ; or if you have got EnCase evidence images, then select to add EnCase evidence files
7. Select the type of image as shown in above image: for Example: Disk
8. Deleted files recovery: EnCase allows for the analysis of data located at various locations on the disk image, such as unallocated space and slack space. With the use of multiple file viewers, files can be quickly searched and identified. , EnCase can also recover remnants of deleted or partially overwritten files.
9. Adding Keywords: Encase provides a search engine to locate information anywhere on the disk image. It is recommended to create a keyword list prior to beginning the case. Starting the Search. EnCase allows GREP (regular expression) search expressions also. We can set keywords by choosing View > Keywords from the main menu.
Search Hits can be found by selecting Cases > Search Hits.
10. By right-clicking and selecting Bookmark, important findings can be bookmarked. The bookmarked data can be accessed directly at Cases > Bookmarks
Here are some tips for using EnCase: