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What you will find in this presentation What is computer forensics? The four As How disk storage works in your case How files live on disk Where evidence.

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Presentation on theme: "What you will find in this presentation What is computer forensics? The four As How disk storage works in your case How files live on disk Where evidence."— Presentation transcript:


2 What you will find in this presentation What is computer forensics? The four As How disk storage works in your case How files live on disk Where evidence might reside What is slack space? What is unallocated space? Hex & Ascii representation Tools Steganography, recovering hidden data Requirements Glossary

3 Digital version of CSI Finds evidence of incidents on digital equipment Computers & drives PDAs iPods Cell phones Digital camera & flash cards Network equipment Evidence must stand up in court

4 Acquire Archive Analyze Attest

5 Crime Scene Considerations Identify and acquire the evidence Safeguard and process physically Prints and trace evidence Handling of Magnetic media (drives and floppies, etc) Keep away from magnets, machinery which generate magnetic fields and static electricity (no plastic evidence bags to generate static electricity) Note where found, under what circumstances Nature of material expands where it might be hidden Between pages of a book Inside a device Locate material which may assist User manuals, lists, password which might be written down

6 Identify sources of information hard drives disks (floppy, CD, DVD) other devices Digital cameras Cell phones PDAs Technician must understand technology required to archive information Once seized as evidence, the technician will then create a bit-for-bit forensic image and make it available to the analyst

7 Image is a bit-for-bit snapshot of the disk This image is used by the analyst The image contains everything on the disk Files, deleted files, dead space on disk, etc… Cant read it directly The forensic software interprets the image and sees all the files on the disk NEVER use the original media unless no other alternative… always use the bit-for-bit image if possible If you ever need to use the original material, document it along with the reason 2008 CSI Challenge Teams will be provided a bit-for-bit image for analysis Your team will not have to create this image

8 Examination of your evidence In Forensic Toolkit (FTK) Create a New or Open an Existing case Add evidence to the case Drive (hard disk, floppy, USB flash drive, etc) Previously acquired bit-image 2008 CSI Challenge teams will use this option A Folder and its contents Individual files

9 Find the evidence Examine the structure of the disk itself hidden data Suspicious files Renamed, altered or deleted Search for strings ( a string is a group of characters, such as a name, credit card number, or even a fragment of a word) in files in deleted files in dead space (slack or unallocated, explained later)

10 Look for stuff in plain sight Files, s, etc Look for hidden evidence Files renamed to appear as different file types Word document renamed as a jpg image file Stegod file (see later) Encrypted files Password required Locate password In existing evidence At crime scene Guess password (important dates, names, etc) Might require personal knowledge about suspects background Crack the password using a computer program (not an option for 2008 CSI Challenge… not enough time)

11 File anomalies (irregularities) File name does not match the file type An internal signature in the file indicates the type of file Signatures are also called magic numbers JFIF inside a file might mean its really a JPG image file and not a text file or whatever the filename indicates File times are inconsistent MAC times (Modification-Access-Creation) Its possible for creation time to be post-modification time, depending on OS and how file copied, etc.. Compressed files (zip or other format) May be passworded, contain many files bundled into one file You should know how to unzip a file if its compressed or zipped File ends

12 Critical thinking: the investigative part! incriminating evidence (or exculpatory… excluding a suspect) discovering new avenues of inquiries s Recently used documents visited websites Snippets or fragments of information Including slack space…

13 Saving the evidence for future use once youre done with the case In case you need to review your work

14 Reporting of analysis results written competency Testimony expert witness verbal and non-verbal skills Any reporting of results by 2008 CSI Challenge teams should be clear, legible, using whole sentences to state your findings

15 This is a basic explanation of how information is stored on a computers disk Byte The basic unit of storage Roughly equivalent to a character 1,000,000 byte =1 Megabyte (1 Mb) Holds about a million typewritten characters Sector How bytes are organized on disk 512 bytes per sector Cluster A group of sectors Floppy disk: 1 sector per cluster Hard drive: depends on system

16 Sectors are grouped into clusters a cluster can be 1 sector/cluster(512 bytes) 2 sectors/cluster(1024 bytes) 4 sectors/cluster(2048 bytes) 8 sectors/cluster(4096 bytes) on a floppy, we use one sector / cluster when we need space for a file, the system gives us a cluster (not just a sector)

17 When we write a file using a cluster We have left over room in the cluster This is called slack space Information can reside in slack space Cannot say that the person who wrote the file in that cluster also put that slack information into that cluster Clusters can be reused once a file is deleted Theyre put back into a pool of unallocated clusters (they dont belong to any file) If these clusters havent been used for writing a new file, its possible to recover this deleted file

18 Cluster (512 bytes) we write about 100 bytes the rest is slack This is an example of a cluster containing information….blah blah blah…Dear Sir; We have read your proposal, and … no thanks File Slack

19 No, for the 2008 CSI Challenge you might see hexadecimal notation of the disks data, along with the English readable data This is presented so that youll recognize it when you see it while using FTK (see the next screen) You will not be responsible for knowing hex Computers really only know numbers Certain numbers (values) are associated with letters of the alphabet For example a value of 44 in hexadecimal is a capital D, and a hex 20 is a space, a 64 value is a small d This is called the ASCII code

20 Upper Case D

21 Software such as FTK (which you will be using) contain tools that allow you to: Acquire an evidence image Identify deleted files Possibly recover a deleted file Search the bit image Search for string of text (last name, etc) Identify files containing the string Identify that area as belonging to a file, or in slack space Examine attributes of files Hidden Deleted File times Mismatch between file name and actual file type bad signature (txt file might actually be a jpg file) Show thumbnails of picture type files Export files (or fragments) (collect them in one spot) Bookmark critical findings (highlight relevant findings) Document case for report (times, investigator, etc)

22 Existing software Word, Adobe, etc Open files of that format Analyst must know how the application software works PKZIP, WinZip, WinRAR Extract compressed files Steganograhpy (S-Tools) Extract files from a stegod file S-Tools will use BMP, GIF or WAV files as containers to hide other files Can be used to reveal and extract hidden files

23 Forensic ToolKit (AccessData) Demo version allows examination of cases with a max of 5000 files Add your evidence image file Analyze it Document your results You will use FTK to add your evidence to a new case and analyze it

24 Hidden information inside a file A file inside a file (container file and message file) Can be passworded / encrypted The container (stegod) file is either a bmp or gif image type Can also be an audio file On a hard drive, or on someones iPod, etc… Files can be included in a Word (or other document), such as webpages or be a standalone file on someones hard drive S-Tools can be downloaded to reveal stegod evidence

25 Laptop CD / ROM drive Software Windows XP or Vista Microsoft Office (2003 or better) Access Datas Forensic ToolKit (FTK) S-tools WinZip or capability to unzip files on your drive Should already be built into Windows when you right-click on a zipped filename Tutorials (including this) can be found on the website

26 ASCII Computers only know numbers. ASCII is a code that associates numbers with letters or characters of the alphabet. Bit Binary digit; a one or a zero Byte Grouping of eight bits, representing a numerical value from 0 to 255 Can also represent a character or letter of the alphabet

27 Bit-for-bit image Also known as a bitstream image A snapshot of a piece of evidence, taken in a forensically sound manner (no alteration of original evidence) Bitstream image See bit-for-bit image

28 Cluster A group of sectors. Files are written by the system using clusters Floppy clusters are 1 sector per cluster Hard drives vary (common to find 8 sectors / cluster) Compression (of files) a method of making a large file smaller, by eliminating repetitive sequences of characters See zip files

29 Encryption Used to make information unreadable unless you have a password Evidence Something that provides proof Could be a hard drive, floppy, USB device, paper notes or anything containing information Hexadecimal Numerical representation used by computer scientists. See ASCII code

30 Password A mechanism which prevents a person from accessing a file unless a user provides the correct password or passphrase. Slack or slack space That area of a cluster belonging to a file, which is left over. Information can be contained in slack space. Steganography Hidden writing. The process of hiding information inside a container file. The container picture typically looks no different after having hidden data inside it. Software such as S-Tools is used both to hide as well as reveal information.

31 Zip file A compressed file. A zip can contain a single file, or many files. The zip file can contain a directory (folder) structure, along with all the files in that folder. Zip files can also be passworded.

32 Good luck to all contestants End of PowerPoint presentation

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