Network Security

• Purpose and functionality of common utility software

  • Encryption software
  • Defragmentation software
  • Data compression software
• Operating systems provide some core functions such as memory management
• Utility software

  Programs that perform extra functionality and housekeeping tasks that keep computers running efficiently
• Encryption software

  Software used to encode text so that it cannot be read without knowing the key to decode it
• You can tell if a connection to a website is encrypted by The lock symbol and related URL containing “https”
• Encryption software utilities are commonly used for

  • Encrypt entire hard disks
  • Encrypt files and folders on portable disk
  • Encrypt communication with websites
  • Encrypt data in an organisation's database
• When a large file is saved, it may not fit on the disk in consecutive memory locations and is referred to as 'fragmented'
• In order to read a fragmented file, the drive head will need to move to more locations, making it far slower to access files and programs
• Defragmentation


  Reorganising files so they are stored together, making read times far faster and free space in one place so new files do not need to be fragmented
• Data compression software


  Utilities that enable users to compress and decompress files or folders, reducing the amount of storage space needed on a disk and data sent
• Compression may allow attachments to be sent via email that would otherwise have been larger than a file-size limit
• More data can be stored on backup media with data compression
• Utility software perform extra functionality beyond the core features of an operating system and are used for housekeeping and to help keep the system secure
• Compression software will reduce a file's file size
• Encryption software will encode a file so that it cannot be read without a decryption key
• Defragmentation software will put all fragments of a file together so that the file can be read faster
• System software


  The software that provides a platform for other software to work
• Types of system software

  • Operating systems
  • Utility programs
• Operating system


  Software that provides a platform for other software to work
• System software


  • Application Software
  • Operating systems
  • Utility programs
  • Program translators
• Microsoft Windows


  • An example of an operating system
• What does an operating system do?


  • Provides a platform to allow applications to run and interact with the hardware of the computer
  • Manages the memory, files, transfer of data
  • Operates and controls data flow to graphical display, other input/output devices (printers, speakers, monitor, mouse, keyboard etc...)
• What does the operating system do?

  1. Transfers data between memory locations and the CPU

  2. Produces the visual display for the monitor

  3. Controls peripherals (input/output) such as printers and input devices

  4. Provides a set of programming tools to allow programs to run properly (Application Programming Interface or API)
• Functions of the operating system

  • Memory management - making sure applications have their own space in RAM, releasing memory when programs close
  • Provides a user interface to allow the user to access the computer hardware
  • Manages peripherals controlling input and output signals to/from keyboard, mouse, monitor, printer
  • File management - keeps an index of file locations and free space, allows users to move/edit/delete files
  • User management - manages user logins, passwords, access rights
• User interface


  A method for users to interact with a computer
• Graphical user interface (GUI)


  A type of user interface
• Features of GUIs


  • Windows
  • Icons
  • Menus
  • Pointers
• Graphical user interfaces


  Optimised for mouse or touch screen, intuitive/easy to use
• Command line interface


  Text commands are entered into the computer
• Command line interfaces


  • Require very little processing power, save on need for expensive graphics card, require less hard disk and RAM
  • Allow expert users to perform many useful tasks by chaining commands together, which can be saved in batch files
• CLI vs GUI


  CLI can be faster and more flexible, but harder to use and less intuitive, especially for non-expert users. GUI requires more memory/processing power.
• An advanced computer user makes use of a command line interface
• Steps to delete all Python files from a folder using a GUI

  Move mouse, click buttons, press keyboard
• Kernel


  The core component of an operating system
• Components of an operating system

  • Kernel
  • CPU
  • Memory
  • Devices
  • Applications
  • Drivers
• Memory management


  Copying programs and data from storage into main memory (RAM) to run
• How memory management works

  1. Data is split into "pages" of a certain size

  2. Programs allocated required number of pages in RAM/cache memory

  3. Operating system keeps track of program/data locations in memory, releases memory when programs close
• Virtual memory


  Operating system copies inactive programs/data from RAM to secondary storage to free up space for new programs
• Multitasking


  Operating system manages many tasks happening at the same time, switching CPU/memory resources between them
• User management


  Operating system responsible for user logins, passwords, access rights