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Digital Forensics. Dr. Bhavani Thuraisingham The University of Texas at Dallas Lecture #12 Computer Forensics Analysis/Validation and Recovering Graphic Files October 1, 2008. Outline. Topics fir Lecture #12 What data to collect and analyze Validating forensics data
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Digital Forensics Dr. Bhavani Thuraisingham The University of Texas at Dallas Lecture #12 Computer Forensics Analysis/Validation and Recovering Graphic Files October 1, 2008
Outline • Topics fir Lecture #12 • What data to collect and analyze • Validating forensics data • Data hiding techniques • Remote acquisitions • Recovering Graphic files • Data compression • Locating and recovering graphic files • Stgenaography and Steganalysis • Reference: Chapter 9 am 10 of Textbook • Topics for Lecture Number #13
What data to collect and analyze • Depends on the type of investigation • Email investigation will involve network logs, email server backups • Industrial espionage may include collecting information from cameras, keystrokes • Scope creep: Investigation extends beyond the original description due to unexpected evidence
Validating forensic data • Validating with hexadecimal editors • Provides support such as hashing files and sectors • Discriminating functions • Selecting suspicious data from normal data • Validating with forensics programs • Use message digests, hash values
Data Hiding • Data hiding is about changing or manipulating a file to conceal information • Hiding partitions: Create partitions and use disk editor to delete reference to it, then recreate links to find the partition • Marking bad clusters: Placing sensitive or incriminating data in free space; use disk editors to mark good clusters as bad clusters • But shifting: Change bit patterns or alter byte values • Using Stereography to hide data (Lecture 13) • Encrypt files to prevent access • Recover passwords using passwords recovery tools
Remote Acquisitions • Tools are available for acquiring data remotely • E.g., Diskexplorer for FAT • Diskexporer for NTFS • Steps to follow • Prepare the tool for remote acquisition • Make remote connection • Acquire the data
Recovering Graphic Files • What are graphic files • Bitmaps and Raster images • Vector graphics • Metafile graphics • Graphics file formats • Standards and Specialized • Digital camera file formats • Raw and Inage file format
Data Compression • Lossless compression • Reduce file size without removing data • Lossy compression • Reduces file size but some bits are removed • JPEG • Techniques are taught in Image processing courses
Locating and Recovering Graphic Files • Identify the graphic file fragments • If the file is fragmented, need to recover all the fragments carving or salvaging) • Repair damage headers • If header data is partially overwritten need to figure out what the missing pieces are • Procedures also exist form recovering digital photograph evidence • Steps to follow • Identify file • Recover damage headers • Reconstruct file fragments • Conduct exam
Steganography • Steganography is the art of covered or hidden writing. • The purpose of steganography is covert communication to hide a message from a third party. • This differs from cryptography, the art of secret writing, which is intended to make a message unreadable by a third party but does not hide the existence of the secret communication.
Topics for Lecture #13 • Steganography • Null Ciphers • Digital Image and Audio • Digital Carrier Methods • Detecting Steganography • Tools • Reference: • http://www.fbi.gov/hq/lab/fsc/backissu/july2004/research/2004_03_research01.htm • http://en.wikipedia.org/wiki/Steganography • http://en.wikipedia.org/wiki/Digital_watermarking • http://www.garykessler.net/library/steganography.html • http://www.spectrum.ieee.org/aug08/6593
