Viruses on the Internet

Posted By BrokenClaw on February 4, 2008

There are over 10,000 known types of viruses, and countless variations. It has been estimated that as many as one-fourth of all computers connected to the Internet have been infected. Many of those infected machines are part of limited networks, such as a corporate, government, or educational networks, where one infected machine can quickly spread the virus to all of the others. However, that is not to say that home computers are immune. In fact, it has been demonstrated that an unprotected computer (without a firewall), when connected directly to the Internet, for example with a dial-up modem, will become infected within minutes.

The effects of a virus on your personal computing are discussed in a separate article.

When large numbers of computers are under the control of a single hacker or group of hackers, the result is the creation of a robot network, more commonly called a botnet. A computer which can be controlled remotely by a hacker is sometimes called a zombie, so the term zombie network is also used to describe the same situation. Botnets can be made up of a few hundred or a few thousand computers, but there have been documented cases of botnets with over a million computers under the control of a single hacker.

The term bot can also refer to any computerized interaction. Notably, in Internet chat rooms, there are bots which are designed to imitate human conversation. In some circumstances they are intented to be helpful, but most are just another way to conduct spam and phishing schemes.

Quite often the person responsible for the botnet, the hacker, is not the one who actually uses it. They are just the enabler who sells the services of the botnet to others. In fact, sometimes when a virus infects a new machine, the first thing it does is disable other viruses which are already there, in a sort of turf war.

A hacker can command the computers in the botnet to perform a particular task in concert. For example, by having all of the computers try to access a single website simultaneously, it bombards the website’s servers with an overload of traffic, which will cause the website to crash. This activity is called a distributed denial of service (DDoS) attack, because it denies legitimate web traffic from accessing the website, using the distributed power of the botnet. There have been many such cases on the Internet over the years, often politically motivated, and there is not much a web host can do to prevent it.

Another major use of botnets is to send spam and phishing email. By using the distributed power of the botnet, a hacker can send email at an alarming rate, while maintaining the anonymity of the sender. In most cases, the computer owner is unaware that his or her computer is being used in this manner. You might notice that your computer runs slow at times. If you monitor your router, you might see large amounts of data passing out of your computer for no apparent reason. However, most home routers do not routinely have software that gives any useful information in this regard.


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