The Internet

• Key hardware to the Internet

  • A Network Interface Card (NIC): Every device that connects to a network requires it. It’s usually built into the motherboard of the device. Every smartphone, tablet, and laptop has one.
  • A router, which contains a wireless access point (Wi-Fi)
• When computers connect to networks, they each have a unique IP

  (internet protocol) address. Like each house.

  • Each address has a 32-bit number
  • It is usually written in denary with a dot separating each byte
  • The address allows data to be sent to the correct computer
• A problem with IPv4 addresses is that the number of possible IP addresses used to be 2³² which is less than the amount of humans.

  • This was fixed in IPv6, which makes use of 128-bit numbers
  • IPv6 addresses are separated into 8 groups, each containing 4 hex digits and separated by a colon.
  • Example: 0123 : 4567 : 90ab : cdef : 0123 : 4567 : 89ab : cdef
  • Hex digits must be lowercase
  • 4 zeros in a group should be made into a single 0
  • If there is more than 1 group of zeros, the zeros disappear and a “::” replaces it.
  • Example: 10bc:b3:0:0:0:0:0:1a7 turns into 10bc:b3::1a7
• When data is sent through the Internet or a TCP/IP network, it is split up into much smaller quantities known as data packets

  • These packets each store a small amount of data
  • Each packet may take a different route through the network
• Routers are used to send data to a specific destination on a network

  • A home router, also known as a hub, will route packets from one part of a network to another
  • The home router will route packets, but it also:
  • Contains a wireless access point for Wi-Fi connections
  • Connects the local network using a modem
  • Assigns IP addresses to each computer that connects to it
• IP Address Assignments

  A DHCP (Dynamic Host Configuration Protocol) is built to home routers

  • When a new device connects to the network, it’s assigned an IP address by the DHCP server
• Connecting to the Internet

  A router is used to connect a network to the internet

  • In a home network, the router is combined with the modem, wireless access point, and firewall
  • In a large business, the router is likely to be a dedicated item of hardware
  • The computers and devices will then connect to dedicated wireless access points
• Each NIC needs its own Media Access Control Address (MAC Address)

  Every device with Ethernet, Wi-Fi, or Bluetooth has its own unique MAC address.

  MAC addresses are 48-bit addresses allowing for 2⁴⁸ possible devices

  About MAC Addresses

  • MAC addresses are usually written as hexadecimal digits that have each byte separated by colons or dashes.
  • Example: 32-a3-4b-ca-ef-2e
  • The first 3 bytes (32-a3-4b) is a manufacturer code
  • The last 3 bytes (ca-ef-2e) is a serial code
• When a home router (modem) connects to an ISP, it is given a IP address.

  • Sometimes, the ISP will give a different IP address each time the router connects. This is known as a dynamic IP address.
  • If the IP address is always the same, it’s known as a static IP address.
• The main purpose of a web browser is to render web pages
• Features of web browsers

  • Storing bookmarks and favorites
  • Recording user history
  • Allowing use of multiple tabs
  • Storing cookies
  • Providing navigation tools
  • Providing an address bar
• Web browser | Address bar and navigation

  The address bar allows the user to enter a web address.

  Remember that browsers allow navigation like previous page, next page and refresh page.
• Web browser | Bookmarks and favorites

  Users are able to store a list of bookmarks of sites they want to revisit
• Web browser | Browsing history

  Web browsers keep a record of all web pages that users visit
• Web browser | Tabs

  Tabs are a user interface feature that allow many web pages to remain open at the same time

  • The user is able to quickly select different webpages
  • Before tabs were available in web browsers users would have a large number of browser windows open, which was frustrating to use
• Internet vs World Wide Web

  Many people use the terms Internet and Web interchangeably

  
  

  However they are different:

  • The internet is the large global network of networks.
  • It refers to the physical network infrastructure used for the transfer of data.
  • Other services which use the Internet are: FTP (File Transfer Protocol) & VoIP (Voice over IP)
  • The World Wide Web is one service for information sharing that makes use of the internet
• URL Structure

  A web address is technically known as a Uniform Resource Locator (URL)

  https://www.website.com/images/webpage.png

  Protocol: HTTPS

  Domain name: website.com

  Webpage or file: webpage.png

  Hostname: www.website.com

  Path: images/webpage.png
• HTTP and HTTPS

  Hypertext Transfer Protocol is the protocol used to send webpages.

  Hypertext Transfer Protocol Secure is the same, but sends the webpages/form data in an encrypted format.
• Web servers

  Websites and web pages are stored on web servers.

  Commercial web servers are a physical size that allows many of them to be placed inside a server cabinet (in data centers).
• The Domain Name System (DNS) is a global system that maps domain names to IP addresses.

  Browsers ask DNS servers to translate a domain name to an IP address so they know where to send requests.
• How web requests work

  When a user requests a web page, the following happens:

  1. The web browser requests the IP address of the domain name from the DNS server
  2. The server sends the IP address to the web browser
  3. The web browser sends a request to for the web page to the IP address
  4. The web server sends the web page in HTML to the browser
• Cookies are small amounts of data sent to a web browser.

  • The cookie can be thought of as extra files sent with the webpage
  • The cookie data is stored in the browser files so that it is able to be accessed later.

  Some uses for cookies include:

  • Saving personal details
  • Tracking user preferences
  • Holding items in an online shopping cart
  • Storing login details
• Persistent Cookies

  Persistent cookies remain on the computer even if the web browser is closed or the computer is off.

  This allows a user to remain logged into a website or items in a shopping cart not to be lost.

  The programmer of the website will specify the expiry date for the persistent cookie (when the cookie will be deleted)
• Session Cookies

  Session cookies only last for the browsing session.

  They are stored temporarily in the memory and not in secondary storage.

  When the browser window is closed or the computer is turned off, session cookies will be lost.
• When a user enters a URL, the domain name is sent to a DNS server. The DNS server looks up the domain name and sends the associated IP address to the web browser. The web browser now requests the web page to the IP address for the web server. The web server then sends the web page, written in HTML, to the browser.
• Types of Malware:

  • Viruses
  • Worms
  • Trojan horses
  • Spyware
  • Adware
  • Ransomware
• Ways to prevent Malware:

  • Anti-malware
  • Anti-virus
  • Encryption
  • Acceptable use policies
  • Backup and recovery procedures
• Malware stands for Malicious Software

  Malware are executable programs that run on a computer
• Computer viruses infect computers by:

  • Replicating their code in other programs
  • Infecting other computes

  Computer viruses harm the computer by deleting, corrupting or modifying files

  A worm replicates itself in order to spread to other computers

  • They might cause no damage to the attacked computers
  • They slow down networks and computers
• They have a program, game or cracked file which is something the user wants.

  They have negative program code which causes damage, takes control, or provides access to the computer.
• Ransomware is a type of malware that first encrypts the hard drive of a computer.

  • The user is unable to read any files on the computer or run any programs.
  • The user needs to pay a ransom, usually by crypto.
  • If they pay the ransom, their files should be restored. Otherwise, all files will be deleted
  • The motive for this attack is to get money
• Spyware is a type of malware that finds information about users, their computers, or company information and sends it to the hacker.

  Spyware may be hidden inside an app, software, file, or website.
• Adware is a type of malware that displays large numbers of adverts, often through multiple windows

  • In worst cases, new ads appear faster than the user is able to close them
  • The motive is for the hacker to make money from users clicking on the ads
• People who misuse computers are known as hackers.
• There are several ways that hackers can exploit technical vulnerabilities. Common examples are:

  • Unpatched software – if software updates and security updates are not installed then the software can be vulnerable
  • Out of date software – if software, such as antivirus software isn’t regularly updated then it won’t be able to detect the latest viruses
• Social engineering is the ability to obtain confidential information by asking people for it
• Phishing is a type of social engineering technique

  • Emails, texts, or phone calls are sent to users commonly pretending to be from a bank or website
  • The sender's email address may be fake
  • These messages will try to get personal information such as:
  • Usernames
  • Passwords
  • Credit cards details
• What to look out for in emails (for phishing)

  • Greeting: The phishers don’t know your name, only your email address, so there will be no custom greeting
  • The sender’s address is often a variation of a genuine address
  • Forged link: The link looks genuine, but the URL attached to it may not link to the website given.
  • Request for personal information: Real organizations never do this.
  • Sense of urgency: Hackers try to persuade you that something bad will happen if you don’t act fast
  • Poor spelling, grammar, and tone
• Denial of Service (DoS)

  • In a denial of service attack, a hacker will use or infect a computer so that:
  • it sends as many requests to the server as it can (known as a flood)
  • the server can’t respond fast enough so it slows down or goes offline

  A distributed denial of service (DDoS) attack is the same but uses many computers to send the requests
• Man-in-the-middle attack

  A man-in-the-middle attack (MITM) allows the attacker to intercept data communications between the user and the server. The attacker can then:

  • Eavesdrop to find passwords and personal information
  • Add different information to a web page or other communication such as email

  Connecting to unencrypted Wi-Fi makes it easy to perform an MITM attack