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COS/PSA 413

COS/PSA 413

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COS/PSA 413

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  1. COS/PSA 413 Day 3

  2. Agenda • Questions? • Assignment 1 due • Lab Write-ups (project 2-1 and 2-2) due next class • Lab Recap and After Action Report • Begin Discussion on Working with Windows and DOS Systems • Chapter 3 in 1e and Chapter 7 in 2e Guide to Computer Forensics and Investigations, 2e

  3. Lab 1 Recap • Always know what are going to do before you sit down at the forensics workstations • Methodical not “hack and slash” • Requires reading and prior prep • Learn DOS • Most forensics work is down at low levels (not GUI) • http://www.glue.umd.edu/~nsw/ench250/dostutor.htm • Have part of the lab report started before the lab • Know what it is you are looking for Guide to Computer Forensics and Investigations, 2e

  4. Guide to Computer Forensics and Investigations Chapter 3 Working with Windows and DOS Systems

  5. Objectives • Understand file systems • Explore Microsoft file structures • Examine New Technology File System (NTFS) disks Guide to Computer Forensics and Investigations, 2e

  6. Objectives (continued) • Understand the Windows Registry • Understand Microsoft boot tasks • Understand MS-DOS startup tasks Guide to Computer Forensics and Investigations, 2e

  7. Understanding File Systems • Understand how OSs work and store files • CompTIA A+ certification • File system • Road map to data on a disk • Determines how data is stored on disk • Become familiar with file systems Guide to Computer Forensics and Investigations, 2e

  8. Understanding the Boot Sequence • Avoid data contamination or modification • Complementary Metal Oxide Semiconductor (CMOS) • Stores system configuration, data, and time • BIOS • Performs input/output at hardware level Guide to Computer Forensics and Investigations, 2e

  9. Understanding the Boot Sequence (continued) • Make sure computer boots from a floppy disk • Modify CMOS • Accessing CMOS depends on the BIOS • Delete key • Ctrl+Alt+Insert • Ctrl+A • Ctrl+F1 • F2 • F12 Guide to Computer Forensics and Investigations, 2e

  10. Understanding the Boot Sequence (continued) Guide to Computer Forensics and Investigations, 2e

  11. Understanding Disk Drives • Composed of one or more platters • Elements of a disk: • Geometry • Head • Tracks • Cylinders • Sectors Guide to Computer Forensics and Investigations, 2e

  12. Understanding Disk Drives (continued) Guide to Computer Forensics and Investigations, 2e

  13. Understanding Disk Drives (continued) • Cylinder, head, sector (CHS) calculation • 512 bytes per sector • Tracks contain sectors • Number of bytes on a disk • Cylinders (platters) x Heads (tracks) x sectors • First track is track 0 • So if a disc list 79 tracks (like a floppy) does, it has 80 tracks Guide to Computer Forensics and Investigations, 2e

  14. Guide to Computer Forensics and Investigations, 2e

  15. Understanding Disk Drives (continued) • Zoned bit recording (ZBR) • Platter’s inner tracks are smaller than outer tracks • Group tracks by zone • Track density • Space between each track • Areal density • Number of bits on one square inch of a platter Guide to Computer Forensics and Investigations, 2e

  16. Exploring Microsoft File Structures • Need to understand • FAT • NTFS • Sectors are grouped on clusters • Storage allocation units of at least 512 bytes • Minimize read and write overhead • Clusters are referred to as logical addresses • Sectors are referred to as physical addresses Guide to Computer Forensics and Investigations, 2e

  17. Disk Partitions • Logical drive • Hidden partitions or voids • Large, unused gaps between partitions • Also known as partition gaps • Can hide data • Use a disk editor to change partitions table • Norton Disk Edit • WinHex, Hex Workshop • http://www.x-ways.net/winhex/index-m.html Guide to Computer Forensics and Investigations, 2e

  18. Disk Partitions (continued) Guide to Computer Forensics and Investigations, 2e

  19. Disk Partitions (continued) • Disk editor additional functions • Identify OS on an unknown disk • Identify file types Guide to Computer Forensics and Investigations, 2e

  20. Disk Partitions (continued) Guide to Computer Forensics and Investigations, 2e

  21. Guide to Computer Forensics and Investigations, 2e

  22. Disk Partitions (continued) Guide to Computer Forensics and Investigations, 2e

  23. Guide to Computer Forensics and Investigations, 2e

  24. Master Boot Record • Stores information about partitions • Location • Size • Others • Software can replace master boot record (MBR) • PartitionMagic • LILO • Can interfere with forensics tasks • Use more than one tool Guide to Computer Forensics and Investigations, 2e

  25. Examining FAT Disks • FAT was originally developed for floppy disks • Filenames, directory names, date and time stamps, starting cluster, attributes • Typically written to the outermost track • Evolution • FAT12 • FAT16 • FAT32 Guide to Computer Forensics and Investigations, 2e

  26. Examining FAT Disks (continued) Guide to Computer Forensics and Investigations, 2e

  27. Examining FAT Disks (continued) • Drive slack • Unused space on a cluster • RAM slack • Can contain logon IDs and passwords • Common on older systems • File slack • Bytes not used on the sector by the file • FAT16 unintentionally reduced fragmentation Guide to Computer Forensics and Investigations, 2e

  28. Examining FAT Disks (continued) Guide to Computer Forensics and Investigations, 2e

  29. Examining FAT Disks (continued) • Cluster chaining • File clusters are together (when possible) • Produces fragmentation • Tools • Norton DiskEdit • DriveSpy’s Chain Fat Entry (CFE) command • Rebuilding broken chains can be difficult Guide to Computer Forensics and Investigations, 2e

  30. Examining FAT Disks (continued) Guide to Computer Forensics and Investigations, 2e

  31. Guide to Computer Forensics and Investigations, 2e

  32. Deleting FAT Files • Filename in FAT database starts with HEX E5 • FAT chain for that file is set to zero • Free disk space is incremented • Actual data remains on disk • Can be recovered with computer forensics tools Guide to Computer Forensics and Investigations, 2e

  33. Examining NTFS Disks • First introduced with Windows NT • Spin off HPFS • From IBM O/S 2 • Provides improvements over FAT file systems • Stores more information about a file • Microsoft’s move toward a journaling file system • Keep track of transactions • Can be rolled back Guide to Computer Forensics and Investigations, 2e

  34. Examining NTFS Disks (continued) • Partition Boot Sector starts at sector 0 • Master File Table (MFT) • First file on disk • Contains information about all files on disk (meta-data) • Reduces slack space • NTFS uses Unicode • UTF-8, UTF-16, UTF-32 Guide to Computer Forensics and Investigations, 2e

  35. Examining NTFS Disks (continued) Guide to Computer Forensics and Investigations, 2e

  36. NTFS File Attributes • All files and folders have attributes • Resident attributes • Stored in the MFT • Nonresident attributes • Everything that can be stored on the MFT • Uses inodes for nonresident attributes • Logical and virtual cluster numbers • LCN and VCN Guide to Computer Forensics and Investigations, 2e

  37. NTFS Data Streams • Data can be appended to a file when examining a disk • Can obscure valuable evidentiary data • Additional data attribute of a file • Allow files be associated with different applications Guide to Computer Forensics and Investigations, 2e

  38. NTFS Compressed Files • Improve data storage • Compression similar to FAT DriveSpace 3 • File, folders, or an entire volume can be compressed • Transparent when working with Windows XP, 2000, or NT • Need to decompress it when analyzing • Advanced tools do it automatically Guide to Computer Forensics and Investigations, 2e

  39. NTFS Encrypted File System (EFS) • Introduced with Windows 2000 • Implements a public key/private key encryption method • Recovery certificate • Recovery mechanisms in case of a problem • Works for local workstations or remote servers Guide to Computer Forensics and Investigations, 2e

  40. Deleting NTFS Files • Similar to FAT • NTFS is more efficient than FAT • Reclaiming deleted space • Deleted files are overwritten more quickly Guide to Computer Forensics and Investigations, 2e

  41. Understanding the Windows Registry • Database that stores: • Hardware and software configuration • User preferences (user names and passwords) • Setup information • Use Regedit command for Windows 9x • Use Regedt32 command for Windows XP and 2000 • FTK Registry Viewer Guide to Computer Forensics and Investigations, 2e

  42. Understanding the Windows Registry (continued) • Windows 9x Registry • User.dat • System.dat • Windows 2000 and XP Registry • \Winnt\System32\Config • \Windows\System32\Config • System, SAM, Security, Software, and NTUser.dat Guide to Computer Forensics and Investigations, 2e

  43. Understanding the Windows Registry (continued) Guide to Computer Forensics and Investigations, 2e

  44. Understanding Microsoft Boot Tasks • Prevent damaging digital evidence • OSs alter files when computer starts up Guide to Computer Forensics and Investigations, 2e

  45. Windows XP, 2000 and NT Startup • Steps: • Power-on self test (POST) • Initial startup • Boot loader • Hardware detection and configuration • Kernel loading • User logon Guide to Computer Forensics and Investigations, 2e

  46. Startup Files for Windows XP • Files used during boot process: • NTLDR • Boot.ini • BootSec.dos • NTDetect.com • NTBootdd.sys • Ntoskrnl.exe • Hal.dll • Device drivers Guide to Computer Forensics and Investigations, 2e

  47. Windows XP System Files Guide to Computer Forensics and Investigations, 2e

  48. Windows 9x and Me Startup • Windows Me cannot boot to a true MS-DOS mode • Windows 9x OSs have two modes • DOS protected-mode interface (DPMI) • Command prompt from boot menu • Protected-mode GUI • Dos shell in windows • Startup files • Io.sys • Msdos.sys • Command.com Guide to Computer Forensics and Investigations, 2e

  49. Windows 9x and Me Startup (continued) Guide to Computer Forensics and Investigations, 2e

  50. Understanding MS-DOS Startup Task • Io.sys • Loaded after the ROM bootstrap • Finds the disk drive • Provides basic input/output services • Msdos.sys • Loaded after Io.sys • Actual kernel for MS-DOS • Looks for Config.sys Guide to Computer Forensics and Investigations, 2e