Operating Systems and Data Transmission Basics for Digital

Operating Systems and Data Transmission Basics for Digital Investigations

Objectives n n Define and recognize an operating system Identify the different types of operating system interfaces Identify the different components of an operating system Understand identify the different file systems 2

What Is an Operating System? n Simply stated, an operating system is a program that controls how a computer functions q n OS controls how data is accessed, saved, and organized on a storage device Core of the operating system is called the kernel 3

Operating System Functions n An operating system provides: q q q q Some type of user interface Single-user or multiple-user access to applications File management Memory management Job management Device management Security 4

Types of Interfaces n n n A user interface is the way a user communicates with the computer User interface may also be known as a shell Two major interface types: q q Graphical user interface (GUI) Command-line interface (CLI) 5

Categories of Use n Single-user systems q q q n Designed to be used by only one user DOS is a single-user single-tasking system Windows is a single-user multitasking system Multiple-user systems q q Allow multiple users to access the same application Servers and UNIX/Linux are multiple-user systems 6

File and Memory Management n n The OS controls reading, writing, accessing, and modification of data Basic units of file management are files and folders or directories Memory management deals with temporary storage or use of applications and data The OS controls where applications and data are stored in memory 7

Job and Device Management n n Computers can execute only one instruction at a time per processor or CPU The OS controls the order in which tasks or jobs are processed The OS acts as an intermediary between application software and physical hardware The OS uses device drivers to manage hardware devices 8

Security n n The primary method of security is to have the user authenticate his credentials when he logs into a system Newer operating systems are implementing rights and permissions to files and folders to increase security of OS 9

Common Operating Systems n n n DOS Windows Linux UNIX Macintosh 10

DOS and Windows 3. X n n n DOS was one of the first personal computer operating systems Command-line interface required users to know DOS commands and syntax Windows 3. 1 was the first stable GUI from Microsoft Windows 3. 1 was an application on top of DOS rather than a true operating system Windows 3. 11 added network capability 11

Windows 95 and Windows 98 n Windows 95 innovations include q q q Plug and play Registry Network and Internet capability n Windows 98 enhancements include q q Power management features Upgrade capability via the Internet Automated registry checks and repairs Upgraded plug and play support 12

Windows NT n Windows NT (New Technology) innovations include: q q q Privileged mode, which allows NT to isolate applications so one can be shut down without affecting others Support for multiple CPU processors Multilayered security functions such as n n n File and folder access protection via permissions Network share protection and auditing capability Use of domain controllers 13

Windows 2000 n Windows 2000 based on NT technology with some improvements in the areas of security and networking: q q q Group policies Secure authentication File encryption 14

Windows XP n n n Same kernel as Windows 2000 New GUI, simple firewall, remote control access, and increased speed of OS Versions: XP Home, XP Professional Server versions: Server 2003 XP Home is the upgrade path from Windows ME 15

Windows Vista, 7, and 8 n n n Vista did offer several security enhancements over Windows XP, but the way Microsoft went about those enhancements was problematic. Users were hassled by frequent pop-ups, with cryptic messages that only seemed to complicate matters. User Account Control, App. Locker, Bit. Locker, System Application Permissions, Action Center, Windows Defender 16

Linux n n Linux is a relatively new OS based on the UNIX OS Linux advantages: q q Free or inexpensive Can run on older equipment Can run a multitude of hardware platforms Fast and stable 17

UNIX n n Most operating systems can trace their roots to UNIX Two main “camps” in the UNIX world: q q n n Berkeley Software Distribution (BSD) System V Release 4 (SVR 4) UNIX is a true multi-user multitasking OS designed with security in mind UNIX can use either a CLI or GUI 18

Macintosh n n n Macintosh was the first stable GUI and still the most intuitive GUI on the market Initial Apple philosophy was tight control over hardware and software Apple changed processors which allows a Mac to also run Windows XP 19

Common File System Types n n Function of a file system is to manage files and folders on a system The OS performs the following to help with this: q q q Partitions and formats storage devices Creates a standard for naming files and folders Maintains the integrity of files and folders Provides for error recovery Provides for security of the file system 20

Common File System Types (Cont. ) n FAT (file allocation table) file system q q n File allocation table is a directory the OS uses to keep track of where files are Root directory is the top directory on a FAT system FAT 16 q q q Uses 16 bits in the file allocation table Uses the 3 -character extension to identify file type Can assign attributes to files and folders 21

Common File System Types (Cont. ) n FAT 32 q q q Expands the capabilities of FAT 16 Designed to accommodate large hard drives Designed to use space more efficiently 2 terabyte limit on partition size 4 GB file size (double FAT 16) 22

Common File System Types (Cont. ) n NTFS (New Technology File System) introduced the following features: q q q q Long file name support Ability to handle large storage devices Built-in security controls POSIX support (set of standards that was created to enhance the portability of applications between computer systems) Volume striping File compression Master file table (MFT) 23

Common File System Types (Cont. ) n UNIX/Linux q q q Can handle many different file systems UNIX file system (UFS) is most native format Extended file system (EXT) is primarily used by Linux UNIX uses inodes, storage of information about files on UNIX systems To access the actual file system, a superblock (contains info about blocks, sectors, and cylinder groups on the file system) is created 24

Summary n n n The operating system is the program that controls the basic functions of a computer The OS is the intermediary between the hardware and the software of a computer Two types of interfaces q q Command line (CLI) Graphical user (GUI) 25

Summary (Cont. ) n Functions basic to an OS: q q q n File management Memory management Job management Device management Security management There a variety of operating systems: q Windows, UNIX/Linux, Macintosh, DOS 26

Summary (Cont. ) n Various file systems are used: q FAT 16, FAT 32, NTFS, EXT, UFS, etc. 27