• Internet is a collection of computers connected by network cables or through satellite links is the global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link devices worldwide. Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), electronic mail, telephony, and file sharing.
  • An Internet service provider (ISP) is an organization that provides services for accessing, using, or participating in the Internet. Internet service providers may be organized in various forms, such as commercial, community-owned, non-profit, or otherwise privately owned.
  • Intranet: An intranet is a private network accessible only to an organization's staff. Intranet is system in which multiple PCs are connected to each other. PCs in intranet are not available to the world outside the intranet.
  • An extranet is a controlled private network that allows access to partners, vendors and suppliers or an authorized set of customers � normally to a subset of the information accessible from an organization's intranet.
  • A domain name is an identification string that defines a realm of administrative autonomy, authority or control within the Internet. Domain names are formed by the rules and procedures of the Domain Name System (DNS).
  • A protocol is a set of rules and guidelines for communicating data. Rules are defined for each step and process during communication between two or more computers. Networks have to follow these rules to successfully transmit data.
  • Various Protocols:
    1. IP: Internet Protocol
      The Internet Protocol is where it all begins. IP is responsible for basic networking. The core of the IP protocol works with Internet addresses and every computer on a TCP/ IP network must have a numeric address.
    2. FTP: File Transfer Protocol
      The best known of all protocols outside of IP. The original specification for FTP was compiled by Abhay Bhushan and published April 16 1971. FTP can be defined as a standard network protocol which is especially used to transfer files from one host (machine/ operating system) to another host over a TCP/ IP based network. FTP is hugely insecure when left at its� default settings. To secure FTP the user can connect anonymously but only if the receiving server is configured to allow it. A better and more robust solution is to use FTPS or better still, the SSH File Transfer Protocol.
    3. SSH: Secure Shell
      SSH and FTP are often mentioned in the same breath. Invented in 1995 Secure Shell�s definition is �a cryptographic network protocol for secure data communication�. SSH allows for remote command-line login, and remote execution. It has many of the functions of FTP, but is more secure. The latest versions are referred to as SSH-1 and SSH-2.
    4. SSL: Secure Sockets Layer
      SSL allows security by allowing applications to encrypt data that go from a client to a matching server (for example).
    5. TELNET (telnet)
      The telnet (written in small caps) lets you connect to a remote computer and work as if you were sitting in front of your computer, no matter how far away you are. This is another old technology, first invented in 1969. By default, telnet does not encrypt data sent over the network so use with caution!
    6. SMTP: Simple Mail Transfer Protocol
      The Simple Mail Transfer Protocol is the protocol for Internet email. It transfers email amongst computers. The majority of computers in the wild understand SMTP, but some do not.
    7. POP3: Post Office Protocol
    8. The Post Office Protocol (latest version is �3�) provides basic client/ server features that help the user download email from a POP3 email server to a computer (be it mobile or a desktop). The main purpose of the protocol is to allow users to access their email more freely.
    9. HTTP: Hyper Text Transfer Protocol
    10. OK, if you don�t know this one then we really recommend you start your training from the basics! HTTP is the key protocol for being able to transfer data across the Internet. HTTP allows the transfer of HyperText Markup Language (HTML) and other related scripting languages (like CSS) to travel from servers to browsers.
    11. HTTPS: Hypertext Transfer Protocol Secure
    12. Think of HTTPS and a secure version of HTTP. The Hypertext Transfer Protocol Secure (HTTPS) protocol facilitates a secure communication over a network. Strictly speaking HTTPS is a layer on top of HTTP using SSL (see above).
    13. SIP: Session Initiation Protocol
    14. SIP is a signaling communications protocol, which is commonly used for managing multimedia communications such as voice and video calls over Internet Protocol (IP) networks � i.e. VoIP. SIP is relatively secure but as we demonstrate in our video, it can be compromised using wireshark and a few other tools.

  • Uniform Resource Locators were defined in RFC 1738 in 1994 by Sir Tim Berners-Lee, the inventor of the World Wide Web, and the URI working group of the Internet Engineering Task Force (IETF), as an outcome of collaboration started at the IETF Living Documents Birds of a feather session in 1992.
  • Web browser: A browser is a software application used to locate, retrieve and display content of Web pages, images, video and other files. The browser contacts the Web server and requests information and Web server sends the information back to the Web browser which displays the results on the computer. Example of Web browser are Mozilla firefox, Internet explorer, Google chrome ,epic etc.
  • Search engines are websites that search the internet for you and give you a list of search results. Search engines can search for more than just written information. Example of Search engines are Google, Bing, DuckDuckGo, etc.
  • Computer Network: A computer network allows computers to exchange data, Information and share resources. The connections between computers (nodes) are established using either cable media or wireless media.
    Types of Network There are many types of computer networks, including the following:
    1. Local-Area Network (LAN): The computers are connected in a building or office.
    2. Wide-Area Network (WAN): The computers are connected by telephone lines or radio waves across country or continent.
    3. Metropolitan-Area Network MAN): A network designed for a town or city.
    4. Personal Area Network (PAN): A network contained within a user's home that connects a person's digital devices.
  • Network Topology is the schematic description of a network arrangement, connecting various nodes(sender and receiver) through lines of connection.
    Types of Topolgies:
    • BUS topology:It is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear Bus topology.
    • RING Topology: It is called ring topology because it forms a ring as each computer is connected to another computer, with the last one connected to the first. Exactly two neighbours for each device.
    • STAR Topology: In this type of topology all the computers are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node.
    • MESH Topology: It is a point-to-point connection to other nodes or devices. All the network nodes are connected to each other. Mesh has n(n-1)/2 physical channels to link n devices.
      There are two techniques to transmit data over the Mesh topology, they are :
      1. Routing: In routing, the nodes have a routing logic, as per the network requirements. Like routing logic to direct the data to reach the destination using the shortest distance.
      2. Flooding: In flooding, the same data is transmitted to all the network nodes, hence no routing logic is required.
  • A firewall is a system designed to prevent unauthorized access to or from a private network. Firewalls can be implemented in both hardware and software, or a combination of both. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet the specified security criteria.
  • Common Firewall Techniques:There are several types of firewall techniques that will prevent potentially harmful information from getting through:
    1. Packet Filter
    2. Application Gateway
    3. Circuit-level Gateway
    4. Proxy Server
  • A threat, in the context of computer security, refers to anything that has the potential to cause serious harm to a computer system.
  • A virus is a type of malicious software program ("malware") that, when executed, replicates itself by modifying other computer programs and inserting its own code. When this replication succeeds, the affected areas are then said to be "infected" with a computer virus.
  • Trojan horses: A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically.
  • Worms: A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole.

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