Saturday, May 19, 2007

What is Worm ?

What is Worm ?

A worm,like a virus,is a program that is designed to harm the computer and destroy data stored on a computer.Worms are considered more harmful viruses because they rely less(or not a t all) on human behaviour in order to spread themselves from one computer to another.The computer worm is designed in order to spread themselves from one computer to another.The computer worm is designed to copy itself from one computer to another over a network.This means that computer worms spread itself to many computers over a network.This means that comptuer worms spread much more rapidly than computer viruses do.Worms use parts of an operating systems that are automatic and are ususally invisible to the user.It is common for worms to be noticed only when their uncontrolled replication consumes system resources,slowing or halting other tasks.

How to avoid virus ?

If we follow some simple safety measures,we can easily protect our computers from getting corrupted by viruses.For this keep the following tips in mind:
  • First of all you must prepare yourself against viruses by knowing about their symptoms,behaviour,general working and their common source of origin.
  • On a regular basis collect information about the alteast virus threats.You can find such informationfrom websites like www.s-cop.com and www.symantec.com.
  • Never download files from unfamiliar or doubtful websites.
  • Do not open nay suspicousor unfamiliar email.Simple delete it.
  • Maintain a seperate folder for downloading files from the Internet.Once the download is complete,scan the folder with an anti-virus software.Once the scan is complete,move the file to some other location on your computer.
  • Scan your computer thoroughly on a regular basis and never stop the scanning operations in the middle.
  • Update your anti-virus software regularly fro the Internet to empower it against new viruses.
  • Always scan a floppy disk before using it because it may also contain viruses.
  • Take a regular back-ups of files so that a possible damage is minimized if a virus attack does occur.
  • Create strong passwords so that virus could not guess the password and breach the security settings of your computer.
  • Maintain a strict security level for browsing the internet.
  • Remove files having extension .TMP and .CHK regularly.

Friday, May 18, 2007

Computer Virus

A virus is a piece of programming code usually disguised as a something else that causes some unexpected and usually undesirable event.A virus is often designed so that it is automatically spread to other computers.Viruses can be transmitted as attachments to an e-mail ,as downloads,or be present on a diskette or CD.The source of the e-mail,downloaded file,or diskette you've received is often unaware of the virus.Some viruses wreak their effect as soon as their code is executed;other viruses lie dormant until circumstances cause their code to be executed by the computer .Some viruses are playful in intent while others can be quite harmful,erasing data or causing your hard disk to require re formatting.It must be remembered that a computer virus does not spread on its own,rather it requires some carrier to transport it from one place to another.We send e-mail document attachments,trade programs on diskettes,or copy files to file servers.When the next unsuspecting user receives the infected file or disk ,they spread the virus to their computer,and so on.

Categories of Computer Viruses

There three broad categories of viruses are as follows:

  • File Infectors
  • System Infectors
  • Macro Viruses

File Infectors

Some file infector viruses attach themselves to program files while some can infect any program for which execution is requested.When the program is loaded,the virus is loaded well.Other file Infector viruses arrive as wholly-contained programs or scripts sent as an attachments to an e-mail note

System Infectors

These viruses infect executable code found in certain system areas on a disk.They attach to the DOS boot sector on diskettes or the Master Boot Record on hard disks.A typical scenario (Familiar to the author) is to receive a diskette from an innocent source that contains a boot disk virus.When your operating system is running,files on the diskette can be read without triggering the virus.However,if you leave the diskette in the drive,and then turn the computer off or reload the operating system,the computer will look first in your A drive,find the diskette with its boot disk virus,load it,and make it temporarily impossible to use your hard disk.(Takes several days for recovery).This is why you should make sure you have a bootable floppy.

Macro Viruses

These are among the most common viruses,and they end to do the least damage.Macro viruses infect your Microsoft Word application and typically insert unwanted words or phrases.

Symptoms for a virus

Some common symptoms for a virus are as follows:

  • The computer begins to run slowly.
  • Unusual messages and graphics appear on your screen for inexplicable reasons.
  • Music,not associated with any of the current programs,begins to play.
  • Some of the program and/or data files have either been corrupted,or they have become difficult to locate.
  • Unknown files or sub-directories has been created.
  • The size/dates of executable files change automatically.
  • The computer does not remember CMOS settings.
  • The disk volume label has been changed mysteriously.
  • The sizes of total and free memory are changed unexpectedly.
  • The hardware devices begin to exhibit unusual behavior.

Anti-virus Software

An anti-virus software protects your computer from unexpected virus attack.Apart from protecting your system,anti-virus software performs the following tasks:

  • Detects the name of virus and its type.
  • Detects the name of infected file or folder and mentions the exact location of infected file or folder on your computer and removes the virus from the computer.
  • Most of the anti-virus softwares come with Alert feature.This feature keeps a vigil on your computer and as soon as some virus-like activity is found,the alert featuredisplays a message box and alters the user.
  • By changing the settings of anti-virus,you can instruct it to scan the computer on a regular basis.
  • With regular updates,anti-virus software protects your computer from new viruses.

You can easily purchase an anti-virus software from market or can easily download free version of some anti-virus software from the website.But it si recommended that you purchase a complete and genuine copy of anti-virus software as it comes with future supports for your computer like updating your an anti-virus software against the latest virus threats and various additional features.the names of some popular anti-virus softwares are listed below.

NORTON ANTI-VIRUS

MCAFEE

SMART COP

SPYWARE

REGISTER MECHANIC

Internet Terminology

Some of the commonly used terminologies in the Internet are listed below.


TCP/IP


TCP/IP (The Transmission Control Protocol /Internet Protocol) is the protocol suite that is designed specially for the Internet.Basically ,the TCP/IP handles network communication between network nodes (computers connected to each other over the Internet).The suite is actually composed of several protocols including IP,which handles the movement of data between host computers and TCP which manages the movement of data between applications.


URL

A URL (Uniform Resource Locator) is the address of a resource accessible on the Internet.The type of resource depends on the Internet application Protocol.Using the World Wide Web's protocol -the Hypertext Transfer Protocol(HTTP)-the resource can be an HTML page,an image file,a program such as java applet ,or any other file supported by HTTP.The URL contains the name of the protocol required to access the resource , domain name that identifies a specific computer on the Internet,and a hierarchical description of a file location on that computer.
Here is an example of URL:http://www.dreamtechpress.com/ According to the above-mentioned URL , a web page needs to be accessed by using HTTP (a protocol) that is located on a computer named WWW.dreamtechpress.com It must be remembered here that a URL can be for any web page,not just a home page or any individual file.

HTTP


Hyper Text Transfer Protocol is a protocol used by the World Wide Web.The main web
of HTTP is deals with the message's format and transmission and what actions web servers and browsers should take in response to various commands.For example,when you enter a URL in your browser,this actually sends an HTTP command to the web sever( computer where web pages reside) directing it to fetch and transmit the requested web page.The other main standard that controls how the World Wide Web works is HTML,which deals with how web pages are formatted and displayed.

Modem

Modem is a device that is used to transmit data over the Internet .Your computer sends data in binary code to you modem which converts the binary data into an analog signal.This data then travels along the telephone network.When the data reaches the destination computer ,the modem connected to that computer converts the analog signal back into binary coded data which can be read by your computer.


Network

A networks a group of interconnected systems sharing services and interacting by means of a shared communications link.A network ,therefore,requires two or more individual systems with something to share(data).The individual System must be connected through a physical pathway(called the transmission medium).All systems on the physical pathway must follow a set of communications rules for data to arrive at its intended destination and for sending and receiving systems to understand each other.The rules that govern computer communication are called protocols.

Web Page

The world wide web consists of files , called pages or web pages , which contain information and links to resources throughout the internet.A web pages is an electronic document written in a computer language called HTML(hypertexts markup Language).These web pages are linked together through a system of connections (called hypertext links , hyper links or links), which enable the user to jump from one web page to another by clicking on a link .On the web , the user navigates through these pages of information in accordance of his/her interests.

Website

A website is a set of related (linked through hypertext links) web page, published by an organization or individual .Normally a website contains a home page along with other additional web pages.Each website is owned and updated by an individual , company or organization .It is an area on the web ,which is accessed by its own address (known as URL or the Uniform Resource Locator) . Note that,the quality,detail and style of websites vary enormously ,depending on how it is designed.

Home Page

When you browse the world wide web ,you will often see the term 'home page' .A home page is the starting point or a doorway to the website.Like the table of contents of a book,the home page usually provides an overview of what could be found at the website.If there is not much information ,the home page may be the only page of the website.However,usually you will find at least a few other pages.

Browser

A browser (short for web browser) is a computer program that accesses web pages and display them on the computer screen.It is the basic software that is needed to find ,retrieve ,view , and send information over the internet.In fact,the world wide web,the user requires a web browser.

.The most popular browsers allow are MICROSOFT INTERNET EXPLORER , NETSCAPE NAV
IGATOR ,MICROSOFT INTERNET EXPLORER A
ND MOZILLA FIREFOX



Browsers are of two types:

1.Graphical Browser:Graphical Browser allow retrieval of text,images,audio and video.Navigation is accomplished by pointing and clicking with a mouse on highlighted words and graphics.Both Netscape Navigator and Internet explorer are graphical browsers.

2.Text Browser:Text browser provide access to the web in the text- only mode.Navigator is accomplished by highlighting emphasized words on the screen with the arrow up and down keys and then pressing the enter key to follow the link.Lynx is an example of text-based browser.

Web browser features:

There are many browser s available having different features.However,every browser shares some of the basics features mentioned below:
  • A browser handles requests for HTML files,interprets links, and deals with embedded images ,audio and video elements.
  • A browser keeps the history of the websites visited.
  • A browser lets a user to save a collection of pages , allowing for later retrieval.
  • A browser provides a row of buttons at the top of the browser window for browsing the Internet conveniently .
  • A browser connects to a e-mail program for importing favorites/bookmarks and sending and receiving e-mails from the most commonly used applications and formats.
  • A browser supports web standards currently in use such as HTML,HTTP,JavaScript and Unicode.
  • A browser supports multimedia data in three ways:
  1. Native Support: A browser supports some of the image formats natively .In the other words , a browser presents the image as a part of the web page int the browser window.
  2. Plug-ins: A plug -ins is a program that adds functions to the web browser ,such as an audio player or a compression utility .A plug-in is a set-up within the browser through which it functions properly and correctly.
  3. Helper Programs:Helper Programs are the external applications launched by a web browser or internet client program to view non-native file formats and data types.These programs are not integrated with the browser.
Uniform Resource Locator(URL)

Each web page has a unique address , called a uniform resource locator (URL) that identifies its location on the internet.Web browsers utilize the URL to retrieve a file from the computer on which it resides .Usually , the format of an URL consists of four parts: protocol , sever (or domain) , path and filename.Here is an example,http://www.xyz.com/tutor/start/main.html.

The structure of this URL is
  • Protocol:http
  • Host Computer Name : www
  • Domain Name: com
  • Path : tutor/start/
  • File Name :main.html


The first part of the address , the part before the colon ,is the access method.Most of the time when you see http (hyper transfer protocol) , you are accessing a web page.Apart from http ,you could also find other protocols such as ftp(File transfer Protocol) , news (news server) , mailto(mail server,used for accessing a e-mail server) and telnet (for accessing remote computers ) . The protocol is separated by colons and slashes.After the slashes , the host computer's name is displayed , that is ,an indicator such as www.which stands for World Wide Web.Next comes the name of the computer where the information is located.Note that it is not necessary that all addresses contain www.Although most Internet addresses include a WWW, a web page can reside on the part of the internet that is not found on the world wide web.

After the domain name the domain type is displayed such as com . A domain name is a unique and case sensitive human-readable name for a host on the internet . A domain name type represents the type of organisation or country to which the host belongs.

In addition ,dozens of domain types have been assigned to identify and locate files stored on host computers in countries around the world.These are referred to as two-letter internet country codes , and the have been standardised by the International Standards Organisation (ISO) .For example,uk for united Kingdom , de for Germany au for Australia ,and in for India.The last part of a URL consists of the path and file name .Path name specifies the hierarchic location of the said file on the computer.For instance , in http ://www.xyz.com/tutor/start/main.html is located in start , which is subdirectory of tutor.

Internet Service Provider( ISP )

An Internet service provider (ISP) is an organisation that provides the required software , which is used to connect to the Internet.For a monthly fee, the ISP provides the user software package , username , password , and access phone number(s) . Equipped a modem , the user can then log on to the internet and browse the web.

While choosing an ISP, many factors involved should be kept in mind for subscribing g.First , the user should check the speed and consistency of the internet access. User should also check ISP's reliability , that is, whether the ISP provides consistent access to the internet or does it have frequent down times. Apart from these two criteria , the price of the ISP and other additional services provided by it should also considered .For example , many ISP's provide free web space so that users can create their own website , free e-mail address , and much more.Last but not the least , the user should also check whether the ISP provides a round-the-clock technical assistance.

Web Server

A server is a computer equipped with server software, which provides a specific kind of service to client software running on other computers. The term can refer to a particular piece of software.,for example, a web server ,or to the machine on which the software is running.A web server is a computer that answers requests form user's computers .It serves images and static content , such as web pages , to fill client's ( browser ) requests.Web servers can run on any hardware platform and operating system and store documents in HTML.

To view a website, the browser sends a request to the server.On receiving the request , the server
sends the appropriate web page to the client 's machine .The client's machine (browser) receives the information in the form of HTML commands .The browser interprets the HTML , finds all the pictures (or other types of media) , and displays the information onto the user's screen.

Download and Upload

Download refers to the activity of moving or copying a document , program or other data from the internet or other interconnected computer to one's computer.It si the process of "pulling" information from one computer onto another.For example , while accessing a website , the HTML code and graphics must be downloaded from remote server onto the user's computer , before viewing the website. There are certain files ,which the user downloads a file , he/she is actually copying a particular fiel from the web and placing it on his/her hard drive.

Upload is just opposite to the download .In case of uploading , the user moves or copies a document , program or other data from his./her computer to the internet.Upload refers to the act of moving data from one computer to another , usually to a server or remote computer. For example, a software company may upload a demonstration of its new software onto the web so that users can then download the software onto their individual computers.

Online and Offline

The term online is commonly referred to as connected to the world wide web via internet.When you connect to the internet ,you are online or live.Being online is also used to refer to materials stored on to a computer or to a device like printer that is ready to accept commands from a computer .Hence , any activity undertaken while the computer is connected to another computer or network is said to be online .

Offline is just the opposite of online and it refers to the actions performed when the user is not connected , via telecommunications , to another computer or a network like the internet.Hence , offline means that the user is no longer connected to a remote computer .If a printer or other peripheral is not ready to receive data from the computer ,it is also considered offline,

Equipment Required for an Internet Connection

For using Internet,we need the following equipment:

Computer

Any good IBM compatible ,Macintosh or UNIX computer that has good storage space(2 GB or more) ,atleast 16MB RAM or more and 200MHZ processor.

Modem

Modem is a device that is used to transmit data over the network .Your computer sends data in binary code to your modem which converts the binary-coded data to an analogue signal.This data then travels along the telephone network .When the data reaches the destination computer ,the modem connected to that computer converts the analogue signal back into binary coded data which can be read by your computer .Thus the modem transmits data over the network.
There are two types of modems: External Modem and Internal Modem.

External Modem and Internal Modem

The External Modem has to be connected to your computer and telephone line with cables and electric socket while the Internal Modem is already built inside your computer.The electric socket while the internal Modem is already built inside the computerThe billing meter of your telephone starts moving the moment you get connected to Internet .So a modem with good speed ensures low telephone bills .Modem with a speed of 28,800 bps is recommended ,but you can also use one having a speed of 14,000 bps.

Web Browser

The software used to navigate through the web is known as a browser.The most popular browser types today are Netscape Navigator and Microsoft Internet Explorer 5.0/5.5.Before you start working on the Internet ,make sure youn have a web browser in your
computer ,otherwise you will not be able to surf the net.The Microsoft Internet Explorer comes installed along with MS OFFICE 2000/XP.

Telephone Line

It is essential to have a telephone connection to get connected to Internet .All the data and information pass through the telephone lines as anologue signals,if you use the "call waiting" facility.

Internet Service Provider(ISP)

If you have a computer with a web browser ,a modem and a telephone line connected to your computer ,you now need an Internet connection.You cam get an Internet connection from various Internet Service Providers (ISPs). Earlier in India,Inernet connection was only available through VSNL (VIdesh Sanchar Nigam Limited).Now, you can choose your ISP from among 120 companies which have been granted ISp licenses.Among them ,the most popular ISPs are VSNL,MTNL and Mantra Online

Surfing the Net

You must have heard people talking about Surfing or Browsing the Net.Someone is surfing the net means he or she is checking out sites on Internet.Internet contains a graphical ,easy to use system that offers a vast amount of infromation.This system is the World Wide Web(WWW) or Web.It consists of a huge collection of pages containing information,images,sounds and video clips stored in computers around the world.Each page on WWW is called Webpage.The site which stores webpages is called a Website.Various companies,universities,governmenet agencies,etc have their own websites which contain several webpages of information about the services provided by them.The first page of any website is called Home Page.The web lets you move around different webpages and websites and gather information with a click of your computer mouse.As mentioned earlier,this is called Surfing the net.

Scope of Internet

Considering the vast array of applications available on Internet,one just can't access the reach of its monumebntal capability .No matter wherever you are located,if your computer has an internet connection,you can access any information related to any related to any field,be it computers ,sports,education,movies,etc., from any part of the world .You can even subscribe to mailing lists and engage in online shopping .The most interesting thing about Internet is that no organisation owns or controls it.There is no government regulation and no one censors the information made available on internet.Let us now have a look at a few thing you can do on Internet.

Electronic Mail(E-mail)

Electronic mail is a fast .easy and economical way to send messages to anyone having an Internet account .Through this most widely used feature on Internet you can Exchange messages with your family,friends and business associates around the world. Along with the messsages,one can also send pictures,audio and animation.

Information Storehouse

You can easily access information from Internet from Internet regarding any subject.Internet is very much like a library with enormous information on any subject.

Software and Programs

There are thousands of free programs and softwares available on Internet.You can transfer them to your hard disk through a process called File Transfer Protocol.

Entertainment

Hundreds of simple games are available for free on Internet ,like chess ,football,etc,Internet also allows you to review the current movies as well as indulge in interactive conversation with people around the world.

On-line Shopping/Electronic Commerce

Online Shopping means buying or selling on the Net.You can order goods and services on Internet such as computers,softwares,books,dress,vegetables,etc.

what is internet?

You often friends living at distant places-may be in the neighbouring cities or states or in a far-off country like Australia or canada.After writing the lingers on in ur mind as to whether your letter would reach your friend in time .However,now you need not blther anymore about your friends gettting your letters in time.Internet is here to facilitate easy and faster communication between you and your friends.Internet,apart from removing your worry regarding missing postal letters,also saves your postal charges.The role of postman being played by internet is just one of the myraid applications available on internet.It is in fact,a storehouse of unlimited knowledge on any topic under the sun.This knowledge is also getting updated regularly.
What is Internet ?
Internet is a global collection of computers connected to one other by way of transmission of signal through terrestrials well as microwave lines.This global network links thousands of computers at universities,research institutions ,government agencies and business houses throughout the world .Using a small PC at your home anda telephone connection,you can access information from any place in the world through internet .You can access information on thousands of topics ranging from designing toys to making atomic bombs.Each computer connected to internet can communicate with the other computers .You can send or receive messages or retrieve information.Messages or information sent or received on internet is in the form of files .To exchange information on internet ,the computers connected to internet must be able to communicate with one another.This is done using a language called the Transmission Control Protocol/Internet Protocol (TCP/IP).This protocol acts as a medium of communication among numerous Internet computers .