Viruses

While many computer viruses are mere nuisances that cause a handful of minor problems, "successful" computer viruses often make news headlines worldwide because of the havoc some of them create on the world's computer networks. Many of the most damaging viruses are called "worms," such as 2001's "Code Red" as well as "Slammer," a particularly clever and ruthless worm that, for all practical purposes, crashed the entire Internet 15 minutes after it was launched on January 25, 2003.As an Internet businessperson, you need to aware of what viruses are and how to protect them from infecting your personal computers and networks. A widespread virus can cause Internet business millions in lost revenues, computing downtime, destroyed data, and wasted manpower as employees can't use their computers to work and wages must be paid to computer security experts to clean up after the virus.

Here's a look at how viruses work and the most common ones you're likely to encounter.

Viruses. The word "computer virus" has become a kind of catchall term for any type of maliciously constructed computer code that can attack computers. But specifically, a virus is actually a small computer program, designed to intentionally cause some aspect of a computer to malfunction, which comes imbedded in a larger software program or within a single file.

This process involves inserting the virus code into the larger program's overall code. When a program such as a word processor or spreadsheet, for example, is launched, the virus code is deployed as well, carrying out instructions written by its author to replicate itself and possibly damage data.

A computer virus gets its name because it behaves like a biological virus: it replicates itself and infects other computers it comes into contact with. But unlike biological viruses, computer viruses are always man-made, never created by a malfunctioning computer or program.

Many basics viruses are shockingly simple to create, and do little more than replicate themselves across many computers on a network. It's unusual for simple viruses to cause serious damage to data, but they can quickly gobble up network resources, grinding a computer network to a halt until the viruses can be removed.

Early 1980's forms of viruses, such as boot sector viruses, are practically nonexistent today. These viruses were usually spread by exchanging diskettes, which have been replaced as a storage device by compact discs (CDs) and digital video discs (DVDs), which are highly secure.

Instead, the most-common viruses today are spread as attachments to e-mail messages, tricking the message recipient into double-clicking an executable file (which has an often-hidden .EXE extension). This launches the virus on the computer and then replicates by sending a copy of itself and the message to other e-mail addresses found in the address book of the recipient's e-mail client software.

Most viruses spread by e-mail cause little real damage, but there are exceptions. The so-called "Melissa" virus closed down the e-mail servers of many large companies, including Microsoft whose Microsoft Word the virus exploited to spread itself.

Melissa was included in a Word document uploaded to an Internet newsgroup. Newsgroup visitors, thinking the document was useful, double-clicked it to open it, launching the virus that was sent to the first 50 listings in their address book of their e-mail client. Recipients received an e-mail message, often with their first name in the subject line (gleaned from the address book), tricking them into opening it.

Worms. The term "worm" is usually lumped in with the viruses, although there are some important distinctions. A worm, just like a virus, attaches itself to a program or file. But unlike a virus, a worm is designed to travel across computer networks, using Internet protocols without any participation by computer users. The virus's intention is to replicate itself so quickly that it slows down a network or crashes it. Worms exploited security holes in networks, traveling around one or more networks until its code finds a way to penetrate security measures and reach computers.

The most-notorious worm is Slammer, which just three minutes after it was launched was doubling its numbers every 8.5 seconds as it clogged and shut down computer networks worldwide. Another recent worm, "Blaster," is design to infect computers so others can remotely control their operation.

Trojan horses. A Trojan house is like a virus in that it is hidden within a larger, useful software program. That's why it borrows its name from Greek history: You think you are getting something desirable until it opens and you find out something is trying to attack your computer. Unlike a virus or a worm, a Trojan horse cannot replicate itself. Its purpose is to attack a single computer at a time.

Trojan horses are often found on websites, disguised as a free software download for something useful or fun, like a utility or a game. One well-known Trojan horse, in the ultimate irony, masqueraded as a program for anti-virus protection.

Once downloaded, a Trojan horse can damage data, even erasing a hard drive. Some Trojans even create a way for user to gain control of individual computers.

Macro viruses. A macro virus exploits a feature in software programs, especially word processors and spreadsheets, called a macro. Macros enable users of these programs to record and save a set of keystrokes (usually tedious, often-repeated tasks) that are employed when an assigned shortcut is typed by the user.

When a file containing a macro virus is launched, the virus launches a macro programmed by the author. This usually causes the file to perform fairly harmless buy annoying tasks, such as inserting funny or obscene text when a certain key or key combination is typed.

Macro viruses, like the Melissa virus discussed earlier, are typically spread as attachments to e-mail messages.

Virus prevention. All the talk about viruses and their counterparts shutting down networks, allowing hackers to steal personal information and erasing hard drives can be scary stuff. And, sometimes, it is. But there are many ways you can guard yourself from the vast majority of viruses and their variants, ranging from some commonsense, defensive computing practices to installing software protection.

· Be wary of file attachments. The easiest way to stop many viruses is simply to be careful with e-mail, Internet communications, and downloading files. Since many viruses are spread by e-mail, it's a good idea to never open file attachments from people or companies you don't know or aren't expecting.

Executable files (with an .EXE extension) and Visual Basic files (with a .VBS extension) are particularly suspect, as these are common platforms for delivering viruses, worms and macro viruses.

· Safe downloads. Viruses and, especially, Trojan horses make their way unto computer systems when computer users download questionable software programs. To prevent these attacks, only download files from websites that you are confident are reliable. Also, if you install software from only CDs, the risk of virus infection is miniscule.

· Antivirus software and firewalls. Installing antivirus software and firewalls on personal computers as well as computer networks has done an increasingly good job over the years at stopping virus attacks. Antivirus software blocks viruses, Trojan horses, macro viruses and other variants from attacking computers.

A firewall is a set of programs that protects a network from access outside the network, and the most-popular antivirus software and firewalls titles come from Symantec (www.symantec.com) and McAfee (www.mcafee.com/us).

McAfee's Internet Security Suite 2005 and Symantic's Norton WinAntiVirus PRO 2005 are both security suites with software for antivirus and firewall protection as well as protection from pop-ups, spyware and adware. Another popular option, if you use Windows XP, is Microsoft's Windows Firewall as part of its Service Pack 2 for the XP operating system (http://www.microsoft.com/windowsxp/using/security/internet/sp2_wfintro.mspx).