Working with Windows and DOS Systems.ppt

CHAPTER 6
WORKING WITH
WINDOWS AND DOS
SYSTEMS

2
OBJECTIVES
 Explain the purpose and structure of file systems
 Describe Microsoft file structures
 Explain the structure of New Technology File System (NTFS)
disks
 List some options for decrypting drives encrypted with whole
disk encryption
03/17/25 CH.VijayaBhaskar,SNIST

3
OBJECTIVES (CONTINUED)
 Explain how the Windows Registry works
 Describe Microsoft startup tasks
 Describe MS-DOS startup tasks
 Explain the purpose of a virtual machine

4
UNDERSTANDING FILE SYSTEMS
 File system
… Gives OS a road map to data on a disk
 Type of file system an OS uses determines how data is stored
on the disk
 A file system is usually directly related to an OS
 When you need to access a suspect’s computer to acquire or
inspect data
… You should be familiar with the computer’s platform

5
UNDERSTANDING THE BOOT
SEQUENCE
 Complementary Metal Oxide Semiconductor (CMOS)
… Computer stores system configuration and date and time
information in the CMOS
 When power to the system is off
 Basic Input/Output System (BIOS)
… Contains programs that perform input and output at the
hardware level

6
SEQUENCE (CONTINUED)
 Bootstrap process
… Contained in ROM, tells the computer how to proceed
… Displays the key or keys you press to open the CMOS setup screen
 CMOS should be modified to boot from a forensic floppy disk or
CD

7
SEQUENCE (CONTINUED)

8
UNDERSTANDING DISK DRIVES
 Disk drives are made up of one or more platters coated with
magnetic material
 Disk drive components
… Geometry
… Head
… Tracks
… Cylinders
… Sectors

9

10

11
UNDERSTANDING DISK DRIVES
(CONTINUED)
 Properties handled at the drive’s hardware or firmware level
… Zoned bit recording (ZBR)
… Track density
… Areal density
… Head and cylinder skew

12
EXPLORING MICROSOFT FILE
STRUCTURES
 In Microsoft file structures, sectors are grouped to form clusters
… Storage allocation units of one or more sectors
 Clusters are typically 512, 1024, 2048, 4096, or more bytes each
 Combining sectors minimizes the overhead of writing or
reading files to a disk

13
EXPLORING MICROSOFT FILE
STRUCTURES (CONTINUED)
 Clusters are numbered sequentially starting at 2
… First sector of all disks contains a system area, the boot record,
and a file structure database
 OS assigns these cluster numbers, called logical addresses
 Sector numbers are called physical addresses
 Clusters and their addresses are specific to a logical disk drive,
which is a disk partition

14
DISK PARTITIONS
 A partition is a logical drive
 FAT16 does not recognize disks larger than 2 MB
… Large disks have to be partitioned
 Hidden partitions or voids
… Large unused gaps between partitions on a disk
 Partition gap
… Unused space between partitions

15
DISK PARTITIONS (CONTINUED)
 Disk editor utility can alter information in partition table
… To hide a partition
 Can examine a partition’s physical level with a disk editor:
… Norton DiskEdit, WinHex, or Hex Workshop
 Analyze the key hexadecimal codes the OS uses to identify and
maintain the file system

16

17

18
DISK PARTITIONS (CONTINUED)
 Hex Workshop allows you to identify file headers
… To identify file types with or without an extension

19

20

21
MASTER BOOT RECORD
 On Windows and DOS computer systems
… Boot disk contains a file called the Master Boot Record (MBR)
 MBR stores information about partitions on a disk and their
locations, size, and other important items
 Several software products can modify the MBR, such as
PartitionMagic’s Boot Magic

22
EXAMINING FAT DISKS
 File Allocation Table (FAT)
… File structure database that Microsoft originally designed for
floppy disks
… Used before Windows NT and 2000
 FAT database is typically written to a disk’s outermost track
and contains:
… Filenames, directory names, date and time stamps, the starting
cluster number, and file attributes
 FAT versions
… FAT12, FAT16, FAT32, and VFAT

23
EXAMINING FAT DISKS
(CONTINUED)
 Cluster sizes vary according to the hard disk size and file
system

24
EXAMINING FAT DISKS
(CONTINUED)
 Microsoft OSs allocate disk space for files by clusters
… Results in drive slack
 Unused space in a cluster between the end of an active file and the
end of the cluster
 Drive slack includes:
… RAM slack and file slack
 An unintentional side effect of FAT16 having large clusters
was that it reduced fragmentation
… As cluster size increased

25
EXAMINING FAT DISKS
(CONTINUED)

26
EXAMINING FAT DISKS
(CONTINUED)
 When you run out of room for an allocated cluster
… OS allocates another cluster for your file, which creates more
slack space on the disk
 As files grow and require more disk space, assigned clusters are
chained together
… The chain can be broken or fragmented

27
EXAMINING FAT DISKS
(CONTINUED)

28
EXAMINING FAT DISKS
(CONTINUED)
 When the OS stores data in a FAT file system, it assigns a
starting cluster position to a file
… Data for the file is written to the first sector of the first assigned
cluster
 When this first assigned cluster is filled and runs out of room
… FAT assigns the next available cluster to the file
 If the next available cluster isn’t contiguous to the current
cluster
… File becomes fragmented

29
DELETING FAT FILES
 In Microsoft OSs, when a file is deleted
… Directory entry is marked as a deleted file
 With the HEX E5 (σ) character replacing the first letter of the
filename
 FAT chain for that file is set to 0
 Data in the file remains on the disk drive
 Area of the disk where the deleted file resides becomes
unallocated disk space
… Available to receive new data from newly created files or other
files needing more space

30
EXAMINING NTFS DISKS
 New Technology File System (NTFS)
… Introduced with Windows NT
… Primary file system for Windows Vista
 Improvements over FAT file systems
… NTFS provides more information about a file
… NTFS gives more control over files and folders
 NTFS was Microsoft’s move toward a journaling file system

31
(CONTINUED)
 In NTFS, everything written to the disk is considered a file
 On an NTFS disk
… First data set is the Partition Boot Sector
… Next is Master File Table (MFT)
 NTFS results in much less file slack space
 Clusters are smaller for smaller disk drives
 NTFS also uses Unicode
… An international data format

32
(CONTINUED)

33
NTFS FILE SYSTEM
 MFT contains information about all files on the disk
… Including the system files the OS uses
 In the MFT, the first 15 records are reserved for system files
 Records in the MFT are called metadata

34
NTFS FILE SYSTEM (CONTINUED)

35
NTFS FILE SYSTEM (CONTINUED)

36
MFT AND FILE ATTRIBUTES
 In the NTFS MFT
… All files and folders are stored in separate records of 1024 bytes
each
 Each record contains file or folder information
… This information is divided into record fields containing metadata
 A record field is referred to as an attribute ID
 File or folder information is typically stored in one of two ways
in an MFT record:
… Resident and nonresident

37
(CONTINUED)
 Files larger than 512 bytes are stored outside the MFT
… MFT record provides cluster addresses where the file is stored on
the drive’s partition
 Referred to as data runs
 Each MFT record starts with a header identifying it as a
resident or nonresident attribute

38

39

40

41

42
(CONTINUED)
 When a disk is created as an NTFS file structure
… OS assigns logical clusters to the entire disk partition
 These assigned clusters are called logical cluster numbers
(LCNs)
… Become the addresses that allow the MFT to link to nonresident
files on the disk’s partition

43
NTFS DATA STREAMS
 Data streams
… Ways data can be appended to existing files
… Can obscure valuable evidentiary data, intentionally or by
coincidence
 In NTFS, a data stream becomes an additional file attribute
… Allows the file to be associated with different applications
 You can only tell whether a file has a data stream attached by
examining that file’s MFT entry

44
NTFS COMPRESSED FILES
 NTFS provides compression similar to FAT DriveSpace 3
 Under NTFS, files, folders, or entire volumes can be
compressed
 Most computer forensics tools can uncompress and analyze
compressed Windows data

45
NTFS ENCRYPTING FILE SYSTEM
(EFS)
 Encrypting File System (EFS)
… Introduced with Windows 2000
… Implements a public key and private key method of encrypting
files, folders, or disk volumes
 When EFS is used in Windows Vista Business Edition or
higher, XP Professional, or 2000,
… A recovery certificate is generated and sent to the local Windows
administrator account
 Users can apply EFS to files stored on their local workstations
or a remote server

46
EFS RECOVERY KEY AGENT
 Recovery Key Agent implements the recovery certificate
… Which is in the Windows administrator account
 Windows administrators can recover a key in
two ways: through Windows or from an MS-
DOS command prompt
 MS-DOS commands
… Cipher
… Copy
… Efsrecvr (used to decrypt EFS files)

47
DELETING NTFS FILES
 When a file is deleted in Windows XP, 2000, or NT
… The OS renames it and moves it to the Recycle Bin
 Can use the Del (delete) MS-DOS command
… Eliminates the file from the MFT listing in the same way FAT
does

48
UNDERSTANDING WHOLE DISK
ENCRYPTION
 In recent years, there has been more concern about loss of
… Personal identity information (PII) and trade secrets caused by
computer theft
 Of particular concern is the theft of laptop computers and other
handheld devices
 To help prevent loss of information, software vendors now
provide whole disk encryption

49
ENCRYPTION (CONTINUED)
 Current whole disk encryption tools offer the following
features:
… Preboot authentication
… Full or partial disk encryption with secure hibernation
… Advanced encryption algorithms
… Key management function
… A Trusted Platform Module (TPM) microchip to generate
encryption keys and authenticate logins

50
ENCRYPTION (CONTINUED)
 Whole disk encryption tools encrypt each sector of a drive
separately
 Many of these tools encrypt the drive’s boot sector
… To prevent any efforts to bypass the secured drive’s partition
 To examine an encrypted drive, decrypt it first
… Run a vendor-specific program to decrypt the drive

51
EXAMINING MICROSOFT
BITLOCKER
 Available only with Vista Enterprise and Ultimate editions
 Hardware and software requirements
… A computer capable of running Windows Vista
… The TPM microchip, version 1.2 or newer
… A computer BIOS compliant with Trusted Computing Group
(TCG)
… Two NTFS partitions
… The BIOS configured so that the hard drive boots first before
checking other bootable peripherals

52
EXAMINING THIRD-PARTY DISK
ENCRYPTION TOOLS
 Some available third-party WDE utilities:
… PGP Whole Disk Encryption
… Voltage SecureDisk
… Utimaco SafeGuard Easy
… Jetico BestCrypt Volume Encryption
… SoftWinter Sentry 2020 for Windows XP
 Some available open-source encryption tools:
… TrueCrypt
… CrossCrypt
… FreeOTFE

53
UNDERSTANDING THE WINDOWS
REGISTRY
 Registry
… A database that stores hardware and software configuration
information, network connections, user preferences, and setup
information
 For investigative purposes, the Registry can contain valuable
evidence
 To view the Registry, you can use:
… Regedit (Registry Editor) program for Windows 9x systems
… Regedt32 for Windows 2000 and XP

54
EXPLORING THE ORGANIZATION
OF THE WINDOWS REGISTRY
 Registry terminology:
… Registry
… Registry Editor
… HKEY
… Key
… Subkey
… Branch
… Value
… Default value
… Hives

55
(CONTINUED)

56
(CONTINUED)

57
EXAMINING THE WINDOWS
REGISTRY
 Use ProDiscover Basic to extract System.dat and User.dat from
an image file

58

59
REGISTRY (CONTINUED)

60
 Use AccessData Registry Viewer to see what information you
can find in these files

61

62

63

64
UNDERSTANDING MICROSOFT
STARTUP TASKS
 Learn what files are accessed when Windows starts
 This information helps you determine when a suspect’s
computer was last accessed
… Important with computers that might have been used after an
incident was reported

65
STARTUP IN WINDOWS NT AND
LATER
 All NTFS computers perform the following steps when the
computer is turned on:
… Power-on self test (POST)
… Initial startup
… Boot loader
… Hardware detection and configuration
… Kernel loading
… User logon

66
LATER (CONTINUED)
 Startup Files for Windows XP:
… NT Loader (NTLDR)
… Boot.ini
… BootSect.dos
… NTDetect.com
… NTBootdd.sys
… Ntoskrnl.exe
… Hal.dll
… Pagefile.sys
… Device drivers

67
LATER (CONTINUED)
 Windows XP System Files

68
LATER (CONTINUED)
 Contamination Concerns with Windows XP
… When you start a Windows XP NTFS workstation, several files are
accessed immediately
 The last access date and time stamp for the files change to the current
date and time
… Destroys any potential evidence
 That shows when a Windows XP workstation was last used

69
STARTUP IN WINDOWS 9X/ME
 System files in Windows 9x/Me containing valuable
information can be altered easily during startup
 Windows 9x and Windows Me have similar boot processes
… With Windows Me you can’t boot to a true MS-DOS mode
 Windows 9x OSs have two modes:
… DOS protected-mode interface (DPMI)
… Protected-mode GUI

70
STARTUP IN WINDOWS 9X/ME
(CONTINUED)
 The system files used by Windows 9x have their origin in MS-
DOS 6.22
… Io.sys communicates between a computer’s BIOS, the hardware,
and the OS kernel
 If F8 is pressed during startup, Io.sys loads the Windows Startup
menu
… Msdos.sys is a hidden text file containing startup options for
Windows 9x
… Command.com provides a command prompt when booting to MS-
DOS mode (DPMI)

71
UNDERSTANDING MS-DOS STARTUP
TASKS
 Two files are used to configure MS-DOS at startup:
… Config.sys
 A text file containing commands that typically run only at system
startup to enhance the computer’s DOS configuration
… Autoexec.bat
 A batch file containing customized settings for MS-DOS that runs
automatically
 Io.sys is the first file loaded after the ROM bootstrap loader
finds the disk drive

72
UNDERSTANDING MS-DOS STARTUP
TASKS (CONTINUED)
 Msdos.sys is the second program to load into RAM immediately
after Io.sys
… It looks for the Config.sys file to configure device drivers and other
settings
 Msdos.sys then loads Command.com
 As the loading of Command.com nears completion, Msdos.sys
looks for and loads Autoexec.bat

73
OTHER DISK OPERATING SYSTEMS
 Control Program for Microprocessors (CP/M)
… First nonspecific microcomputer OS
… Created by Digital Research in 1970
… 8-inch floppy drives; no support for hard drives
 Digital Research Disk Operating System (DR-DOS)
… Developed in 1988 to compete with MS-DOS
… Used FAT12 and FAT16 and had a richer command environment

74
OTHER DISK OPERATING SYSTEMS
(CONTINUED)
 Personal Computer Disk Operating System (PC-DOS)
… Created by Microsoft under contract for IBM
… PC-DOS works much like MS-DOS

75
UNDERSTANDING VIRTUAL
MACHINES
 Virtual machine
… Allows you to create a representation of another computer on an
existing physical computer
 A virtual machine is just a few files on your hard drive
… Must allocate space to it
 A virtual machine recognizes components of the physical
machine it’s loaded on
… Virtual OS is limited by the physical machine’s OS

76

77
UNDERSTANDING VIRTUAL
MACHINES (CONTINUED)
 In computer forensics
… Virtual machines make it possible to restore a suspect drive on
your virtual machine
 And run nonstandard software the suspect might have loaded
 From a network forensics standpoint, you need to be aware of
some potential issues, such as:
… A virtual machine used to attack another system or network

78
CREATING A VIRTUAL MACHINE
 Two popular applications for creating virtual machines
… VMware and Microsoft Virtual PC
 Using Virtual PC
… You must download and install Virtual PC first

79
(CONTINUED)

80
(CONTINUED)

81
(CONTINUED)
 You need an ISO image of an OS
… Because no OSs are provided with Virtual PC
 Virtual PC creates two files for each virtual machine:
… A .vhd file, which is the actual virtual hard disk
… A .vmc file, which keeps track of configurations you make to that
disk
 See what type of physical machine your virtual machine
thinks it’s running
… Open the Virtual PC Console, and click Settings

82
(CONTINUED)

83
(CONTINUED)

84
SUMMARY
 When booting a suspect’s computer, using boot media, such as
forensic boot floppies or CDs, you must ensure that disk
evidence isn’t altered
 The Master Boot Record (MBR) stores information about
partitions on a disk
 Microsoft used FAT12 and FAT16 on older operating systems
 To find a hard disk’s capacity, use the cylinders, heads, and
sectors (CHS) calculation

85
SUMMARY (CONTINUED)
 When files are deleted in a FAT file system, the Greek letter
sigma (0x05) is inserted in the first character of the filename in
the directory
 New Technology File System (NTFS) is more versatile because
it uses the Master File Table (MFT) to track file information
 In NTFS, data streams can obscure information that might
have evidentiary value

86
SUMMARY (CONTINUED)
 Maintain a library of older operating systems and applications
 NTFS can encrypt data with EFS and BitLocker
 NTFS can compress files, folders, or volumes
 Windows Registry keeps a record of attached hardware, user
preferences, network connections, and installed software
 Virtual machines enable you to run other OSs from a Windows
computer

Working with Windows and DOS Systems.ppt

More Related Content

Similar to Working with Windows and DOS Systems.ppt (20)

More from ChSamson2 (8)

Recently uploaded (20)

Working with Windows and DOS Systems.ppt