Utilizing Regent University library and Internet resources, research what can and cannot be retrieved from operating systems. For example, is a deleted file retrievable? Share your findings.
Your response(s) should comply with the formatting, content, and word count guidelines, along with the style manual requirements, indicated in the syllabus. 300-400 wrds
https://libguides.regent.edu/az/databases
Guide to Computer Forensics and Investigations Sixth Edition Chapter 5
Working with Windows and CLI Systems
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Guide to Computer Forensics and Investigations Sixth Edition
Chapter 5
Working with Windows and CLI Systems
1
Explain the purpose and structure of file systems
Describe Microsoft file structures
Explain the structure of NTFS disks
List some options for decrypting drives encrypted with whole disk encryption
Explain how the Windows Registry works
Describe Microsoft startup tasks
Explain the purpose of a virtual machine
Objectives
2
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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
When you need to access a suspect’s computer to acquire or inspect data
You should be familiar with both the computer’s OS and file systems
Understanding File Systems
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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) or Extensible Firmware Interface (EFI)
Contains programs that perform input and output at the hardware level
Understanding the Boot Sequence (1 of 3)
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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
Understanding the Boot Sequence (2 of 3)
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Understanding the Boot Sequence (3 of 3)
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Disk drives are made up of one or more platters coated with magnetic material
Disk drive components
Geometry
Head
Tracks
Cylinders
Sectors
Understanding Disk Drives (1 of 4)
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Understanding Disk Drives (2 of 4)
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Understanding Disk Drives (3 of 4)
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Properties handled at the drive’s hardware or firmware level
Zone bit recording (ZBR)
Track density
Areal density
Head and cylinder skew
Understanding Disk Drives (4 of 4)
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All flash memory devices have a feature called wear-leveling
An internal firmware feature used in solid-state drives that ensures even wear of read/writes for all memory cells
When dealing with solid-state devices, making a full forensic copy as soon as possible is crucial
In case you need to recover data from unallocated disk space
Solid-State Storage Devices
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In Microsoft file structures, sectors are grouped to form clusters
Storage allocation units of one or more sectors
Clusters range from 512 bytes up to 32,000 bytes each
Combining sectors minimizes the overhead of writing or reading files to a disk
Exploring Microsoft File Structures (1 of 2)
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Clusters are numbered sequentially starting at 0 in NTFS and 2 in FAT
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
Exploring Microsoft File Structures (2 of 2)
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A partition is a logical drive
Windows OSs can have three primary partitions followed by an extended partition that can contain one or more logical drives
Hidden partitions or voids
Large unused gaps between partitions on a disk
Partition gap
Unused space between partitions
Disk Partitions (1 of 3)
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The partition table is in the Master Boot Record (MBR)
Located at sector 0 of the disk drive
In a hexadecimal editor, such as WinHex, you can find the first partition at offset 0x1BE
The file system’s hexadecimal code is offset 3 bytes from 0x1BE for the first partition
Disk Partitions (2 of 3)
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Disk Partitions (3 of 3)
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File Allocation Table (FAT)
File structure database that Microsoft originally designed for floppy disks
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
Three current FAT versions
FAT16, FAT32, and exFAT (used for mobile personal storage devices)
Cluster sizes vary according to the hard disk size and file system
Examining FAT Disks (1 of 7)
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Examining FAT Disks (2 of 7)
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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’s content and the end of the cluster
Drive slack includes:
RAM slack and file slack
An unintentional side effect of FAT16 allowing large clusters was that it reduced fragmentation
As cluster size increased
Examining FAT Disks (3 of 7)
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Examining FAT Disks (4 of 7)
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When you run out of room for an allocated cluster
OS allocates another cluster for your file
As files grow and require more disk space, assigned clusters are chained together
The chain can be broken or fragmented
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
Examining FAT Disks (5 of 7)
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Examining FAT Disks (6 of 7)
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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
Examining FAT Disks (7 of 7)
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In Microsoft OSs, when a file is deleted
Directory entry is marked as a deleted file
With the HEX E5 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
Deleting FAT Files
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NT File System (NTFS)
Introduced with Windows NT
Primary file system for Windows 10
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
It records a transaction before the system carries it out
Examining NTFS Disks (1 of 3)
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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
Examining NTFS Disks (2 of 3)
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Examining NTFS Disks (3 of 3)
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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
NTFS System Files (1 of 3)
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NTFS File System (2 of 3)
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NTFS File System (3 of 3)
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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
MFT and File Attributes (1 of 7)
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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
MFT and File Attributes (2 of 7)
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MFT and File Attributes (3 of 7)
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MFT and File Attributes (4 of 7)
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MFT and File Attributes (5 of 7)
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MFT and File Attributes (6 of 7)
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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
When data is first written to nonresident files, an LCN address is assigned to the file
This LCN becomes the file’s virtual cluster number (VCN)
MFT and File Attributes (7 of 7)
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For the header of all MFT records, the record fields of interest are as follows:
At offset 0x00 – the MFT record identifier FILE
At offset 0x1C to 0x1F – size of the MFT record
At offset 0x14 – length of the header (indicates where the next attribute starts)
At offset 0x32 and 0x33 – the update sequence array, which stores the last 2 bytes of the first sector of the MFT record
MFT Structures for File Data (1 of 7)
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MFT Structures for File Data (2 of 7)
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MFT Structures for File Data (3 of 7)
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MFT Structures for File Data (4 of 7)
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MFT Structures for File Data (5 of 7)
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MFT Structures for File Data (6 of 7)
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MFT Structures for File Data (7 of 7)
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Alternate data streams
Ways data can be appended to existing files
Can obscure valuable evidentiary data, intentionally or by coincidence
In NTFS, an alternate 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
NTFS Alternate Data Streams (1 of 2)
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NTFS Alternate Data Streams (2 of 2)
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NTFS provides compression similar to FAT DriveSpace 3 (a Windows 98 compression utility)
With NTFS, files, folders, or entire volumes can be compressed
Most computer forensics tools can uncompress and analyze compressed Windows data
NTFS Compressed Files
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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 2000 and later
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
NTFS Encrypting File System (EFS)
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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 a command prompt
Commands:
cipher
copy
EFS Recovery Key Agent
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