Viruses, worms and trojan horses

The Internet is full of fun places and vast amounts of information, but also some dangers. Your computer can be damaged by a computer virus sent through e-mail or through a program downloaded from the Web. If you do not use antivirus software, you run the risk of passing viruses along to other computers as well. If you administer a network without virus protection software, all of the computers on your network might be vulnerable.
A virus is a program that can copy itself and infect various parts of your computer, such as documents, programs, and parts of your operating system. Most viruses attach themselves to a file or part of your hard disk and then copy themselves to other places within the operating system. Some viruses contain code that inflicts extra damage by deleting files or lowering your security settings, inviting further attacks.
A worm is a program that makes copies of itself and can spread outside your operating system; it can copy itself from one computer to another by using e-mail or another transport mechanism. Worms can damage computer data and security in much the same ways as viruses, but are different from viruses in that they copy themselves from system to system.

A Trojan horse is a harmless-looking program designed to trick you into thinking it is something you want, but which performs harmful acts when it runs. It is typically received through downloads from the Internet. Trojan horses do not spread by themselves like viruses and worms. Most virus protection programs only detect a limited number of Trojan horses. A good way to help protect your computer from Trojan horses is to visit only Web sites you trust, and avoid downloading things unless you trust the source as well.

Antivirus programs scan e-mail and other files on your computer for viruses, worms, and Trojan horses. If a virus, worm, or Trojan horse is found, the antivirus program either quarantines it or deletes it entirely before it damages your computer and files.

Some companies that make antivirus programs provide regular updates for viruses. Many antivirus programs have an automatic update capability. When your antivirus software is updated, new viruses are added to a list of viruses to check for, protecting your computer from new attacks. If your antivirus updates are not automatic, we recommend that you check for updates on a frequent basis because new viruses are identified every day. If the antivirus program you are using requires a subscription, we strongly recommended that you keep the subscription current to receive regular updates. If your list of viruses is out of date, your computer is vulnerable to new threats.
There are many antivirus programs on the market. Some that I recommend are:
ESET NOD32 ANTIVIRUS, AVIRA, KASPERSKY ANTIVIRUS, MCAFEE.
These are the best antivirus available in the market.

what are cookies

Cookies are small text files that some websites put on your computer to store a variety of information about you and your preferences. Here are answers to some common questions about cookiesWebsites use cookies to offer a personalized experience to users and to gather information about website use. Many websites also use cookies to store information that provides a consistent experience between sections of the site, such as a shopping cart or customized pages. With a trusted website, cookies can enrich your experience by allowing the site to learn your preferences or allowing you to skip having to sign in every time you go to the website. However, some cookies, such as those saved by banner ads, might put your privacy at risk by tracking sites you visit.
You can block or allow cookies on all websites or you can choose which websites' cookies are allowed.Blocking all cookies can help protect your privacy, but it might limit your experience on some websites. Be selective about which websites you allow cookies for. You can start by blocking all cookies, then allow cookies as needed for websites that you trust.Cookies are stored is in a folder named Cookies which is stored inside the Documents and Settings folder. By default, the path is C:\Documents and Settings\your user name\Cookies.
To delete all the cookies:

Start run command and type cookies and open it in the cookies folder delete all the files except the index fileTemporary, or session, cookies are removed from your computer after you close Internet Explorer. Websites use them to store temporary information, such as items in your shopping cart.
Persistent, or saved, cookies remain on your computer after you close Internet Explorer. Websites use them to store information, such as your sign-in name and password, so that you don't have to sign in each time you go to a particular site. Persistent cookies can remain on your computer for days, months, or even years.

Networking types

Networking is the interconnection of two or more computers for resource sharing. Network models classify networks by size, distance and structure. These models help in understanding the relationship among centralized, distributed and collaborative computing systems. There are three fundamental classifications of network models: They are

Local Area Network (LANs)
Metropolitan Area Network (MANs)
Wide Area Network (WANs)

A LAN links a small group of functionally similar workstations within a local geographic area such as a series of adjacent cubicles or offices on the same floor. Once the network expands to include other floors or divers offices within a metropolitan area, it becomes a MAN. Finally, a WAN is simply a LAN of LANs. WANs expand the boundaries of networking to a global (or even galactic) scale.

Local Area Network (LANs). A local area network combines computer hardware and transmission media in a relatively small area. These systems are usually contained within one department, building or campus. In addition, LANs typically comprise only one transmission media type such as coaxial cable or twisted pair but never both. LANs are characterized by comparatively high-speed communications. These high speeds are possible because LANs use one kind of cable which generally is limited to 5KM or less. MANs and WANs, on the other hand, typically rely on unbound communication media which equates to much slower speeds. LANs occupy a relatively small area, include a relatively small number of machines and the components connect directly to the communication media. LAN hardware gives the system its processing communications, system fault tolerance, and most important, connectivity. LAN software endows the system with productivity, user interface, network management and most important, user transparency.

The two most important components in a LAN are the file server (hardware) and network operating system (software). The data transfer rate ranges from 1 byte to 5 GB pre second. LAN also can act as gateway for internetwork communication and as bridge between two networks. Major advantage of this system is the security provide because no any outsiders can access the resources of a private network.

what are computer viruses

Computer viruses have various names and they are just like pathogenic viruses in medical science. However, the computer virus is a program whereas the pathogenic viruses are not. Millions of computers are affected with virus and damages done by viruses are in terms billions of dollars. In the medical institutions, research institutions, educational institutions, banking institutions, research centers, commercial organizations, desktop publishing companies, government and non-government organizations, etc. the effect of viruses is increasing day by day. In developed countries also the effect of viruses on computers has become a big problem. Some companies are interested in producing Antivirus programs which can remove some viruses. But it is not sure that your computer can still be virus free once it is infected.
Virus is the term used to describe any group of willfully destructive computer programs. The computer viruses destroy the data and computer software. Some computer viruses can damage even the hardware components. The nature of viruses varies. Sometimes, they increase the program size by adding some unnecessary bytes and sometimes they kill some bytes. Thus, their effect cannot be declared unless a particular type is not identified. They dislocate the data, program or destroy vital information resource by ceasing the program components. The viruses possess two major characteristics: they can self replicate and they can transmit themselves to another computer without the knowledge of the user.
A computer virus is a small malicious program written in Assembly language or a system programming language like ‘C’. Its aim is to replicate on computers and cause impediment in the normal functioning of the computer. Viruses differ in their mode of replication and their harmful effects.
The history of virus can be traced to the early 80’s when Gene Burelon, an employee of US security firm placed a virus on the computer network of the firm and managed to destroy 168000 records of database. He lost his job but is still remembered as a pioneer in the virus field. In 1983, Dr Frederick Cohen experimented at the University of Pennsylvania with self replicating code and started to use the term virus.