Plus One Computer Application Notes Chapter 9 Internet

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Kerala Plus One Computer Application Notes Chapter 9 Internet

History of the Internet: the Internet means an international network of networks. The first form of Internet is ARPANET(Advanced Research Project Agency Network) started by the US Department of Defence for their military during 1970’s. In 1989 a team lead by Tim Berners Lee introduced WWW(World Wide Web) by using the protocol HTTP. In 1998, the Internet Corporation for Assigned Names and Numbers (ICANN) was established.

Internet: It is a network of networks. It means that the international network. We can transfer information between computers within nations very cheaply and speedily.

Intranet: A private network inside a company or organisation is called an intranet.
Extranet: It allows vendors and business partners to access the company resources.

The hardware and software requirements for the internet.

  • A computer with a modem (internal/external)
  • A telephone connection
  • An account with an ISP
  • A browser S/W eg: Internet ExplorerorMozilla…

Types of connectivity
There are two ways to connect to the internet. First one dialing to an ISP’s computer or with a direct connection to an ISP.

Dial-up Connection: Here the internet connection is established by dialing into an ISP’s computer. If ISP is not busy they verify the user name and password if it is valid they will connect our computer to the uses Serial Line Internet Protocol (SLIP) or Point to Point Protocol (PPP). It is slower and has a higher error rate.

Direct connection: In direct connection, there is a fixed cable or dedicated phone line to the ISP. Here it uses ISDN (Integrated Services Digital Network) a high-speed version of a standard phone line. Another method is leased lines that uses fibre optic cables. Digital Subscribers Line (DSL) is another direct connection, this uses copper wires instead of fibre, optic for data transfer. Direct connection provides high-speed internet connection and error rate is less. Fibre To The Home(FTTH) uses optical fibers for data transmission.

Wireless broadband connectivity
a) Mobile broadband: Accessing the Internet using wireless devices like mobile phones, tablet, USB dongles.

b) Wi-MAX(Wireless Microwave Access): It uses microwaves to transmit information across a network in a range 2 GHz to 11 GHz over very long distance.

c) Satellite broadband: Accessing internet through satellite. A Very Small Aperture Terminal(VSAT) dish antenna and transceiver and modem are required at the user’s location. Expensive and high speed.

Internet access sharing methods:
One Internet connection can be shared among several computers using a LAN, Wi-Fi or Li-Fi
a) Using LAN: The Internet connection in a LAN can be shared among other computers in the network

b) Using Wi-Fi (Wireless Fidelity): It uses radio waves to transmit information across a network in a range of 2.4 GHz to 5 GHz in short distance. Nowadays this technology is used to access the internet in campuses, hypermarkets, hotels by using Laptops, Desktops, tablet, mobile phones etc

c) Using Li-Fi(Light Fidelity) network: It is a fast optical(uses visible light for data transmission) version of Wi Fi. Its main component is a LED. lamp that can transmit data and a photodiode that acts as a receiver.

Services on the Internet
a) www – World Wide Web – This means this website address is unique and can be accessed each nook and corner of the world.

b) A browser is a piece of software that acts as an interface between the user and the internal working of the. internet. With the help of a browser the user can search information on the internet and it allows user to navigate through the web pages. The different browsers are

  • Microsoft internet explorer
  • Mozilla Firefox
  • Netscape Navigator
  • Google Chrome
  • Opera

c. Web Browsing:

  1. The browser determines the URL entered.
  2. The browser asks the DNS for URLS corresponding IP address (Numeric address)
  3. The DNS returns tne address to the browser.
  4. The browser makes a TCP connection using the IP address.
  5. then it sends a GET request for the required file to the server.
  6. The server collects the file and send it back to the browser.
  7. The TCP connection is released.
  8. The text and the images in the web pages are displayed in the browser.

Search engines
By using search engines we will get a variety of information. It is a newly developed tool that helped to search the information on the internet more effectively and easily. Search engines are programs that help people to locate information from crores of website on internet using a database that consists of references. Users can interact with the search engine through the home page of the search engine. To get the information about artificial intelligence just type this in the box provided for it and click the search button. Search engines searches by using a particular search algorithm then displays the matching documents or web addresses. Search engine use soft wares called spiders or bots to search documents and their web addresses. Spiders search the internet using the directions given by the search engines and prepare an index and stores it in a database. The searching algorithm searched this database when the users submits a request and create a web page displaying the matching results as hyperlinks.
Eg: Google, Yahoo, Rediff etc.

Email(Electronic mail) : It is used to send text, multimedia messages between computers over internet. An example of an email id is Here jobi_cg is the user name, rediffmail is the website address and .com is the top-level domain which identifies the types of the organisation. To send an email we require an email address. Some websites provide free email facility. To send an email first type the recipient’s address and type the message then click the send button. The website’s server first check the email address is valid, if it is valid it will be sent otherwise the message will not be sent and the sender will get an email that it could not deliver the message. This message will be received by the recipient’s server and will be delivered to the recipient’s mailbox. He can read it and it will remain in his mailbox as long as he will be deleted. Simple Mail Transfer Protocol(SMTP) is used.

The email message contains the following fields.

  1. To: Recipient’s address will be entered here. Multiple recipients are also allowed by using coma.
  2. CC: Enter the address of other recipients to get a carbon copy of the message.
  3. bcc: The address to whom blind carbon copies are to be sent. This feature allows people to send copies to third recipient without the knowledge of primary and secondary recipients.
  4. From: Address of the sender
  5. Reply to: The email address to which replies are to be sent.
  6. Subject: Short summary of the message.
  7. Body: Here the actual message is to be typed.

The advantages of email are given below:

  • Speed is high
  • It is cheap
  • We can send email to multiple recipients
  • Incoming messages can be saved locally
  • It reduces the usage of paper
  • We can access the mailbox anytime and from anywhere.

The disadvantages are:

  • It requires a computer, a modem, software, and an internet connection to check the mail.
  • Some mails may contain viruses
  • Mailboxes are filled with junk mail. So very difficult to find the relevant mail.

a. Social media: Various social media are Internet forums, social blogs, microblogs etc.

  1. Internet forums: It is an online discussion site where people can exchange information about various issues like social, political, educational, etc in text form.
  2. Social blogs: Conducting discussions about particular subjects by entries or posts.
  3. Microblogs: It allows users to exchange short messages, multimedia files etc.
  4. Wikis: In this, we can give our contributions regarding various topics.
  5. Social networks: By using these websites we can post our data and view others’ data.
  6. Content communities. By using these websites we can share multi-media files.

b. Advantages of social media.

  • Bring people together: It allows people to maintain the friendship
  • Plan and organize events: It allows users to plan and organize events.
  • Business promotion: It helps the firms to promote their sales.
  • Social skills: There is a key role of the formation of society.

c. Disadvantages.

  • Intrusion to privacy: Some people may misuse personal information.
  • Addiction: sometimes it may waste time and money.
  • Spread rumours: The news will spread very quickly and negatively.

Cyber Security: It is used to provide protection of valuable information such as credit card information from unauthorized access, intentional access, deletion etc. while shopping on the internet.

Computer virus: A virus is a bad program or harmful program to damage the routine working of a computer system. It reduces the speed of a computer. It may delete the useful system files and make the computer useless.

Worm: It is a stand-alone malware program that replicates itself in order to spread to other computers. It slows down the traffic by consuming the bandwidth. In 2000 a worm called “ILOVEYOU” is affected by many computers.

Trojan horse: It appears as useful software but it is harmful software and it will delete useful software or files.

Spams: Sending an email without the recipient’s consent to promote a product or service is called spamming. Such an email is called spam.

Hacking: It is a process of trespassing computer networks. Two types of white hats and black hats. White hats hack the computer networks to test the security but black hats intentionally stealing valuable data or destroying data.

Phishing (Fishing): It is an attempt to get other information such as usernames, passwords, bank a/c details etc by acting as the authorized website. Phishing websites have URLs and home pages similar to their original ones and mislead others it is called spoofing.

Denial of Service(DoS) attack: Its main target is a Web server. Due to this attack, the Web server/computer forced to restart and this results in refusal of service to the genuine users. If we want to access a website first you have to type the website address in the URL and press the Enter key, the browser requests that page from the webserver. Dos attacks send a huge number of requests to the web server until it collapses due to the load and stop functioning.

Man in the Middle attacks: It is an attack in which an attacker secretly intercepts electronic messages sent by the sender to the receiver and then modifies the message and retransmit it to the receiver. To prevent this type, of attack encrypted connections such as HTTPS(HTTP Secure), SFTP(Secure FTP), etc, must be used, which will be displayed in the URL.

Preventing network attacks
Firewall: It is a system that controls the incoming and outgoing network traffic by analyzing the data and then provides security to the computer network in an organization from another network (internet)

Antivirus scanners: It is a tool used to scan computer files for viruses, worms, and Trojan horses and cure the infected system. If any fault found it stops the file from running and stores the file in a special area called Quarantine(isolated area) and can be deleted later.

Cookies: Cookies are small text files that are created when we visit a website that keeps track of our details. This information will help the hacker to use it for malicious purposes. It acts like spyware.

Guidelines for using computers over the internet

  • Emails may contain Viruses so do not open any unwanted emails
  • Download files from reputed sources(sites)
  • Avoid clicking on pop-up Advt.
  • Most of the Viruses spread due to the use of USB drives so use cautiously.
  • Use a firewall in your computer
  • Use anti-virus and update regularly
  • Take backups in regular time intervals