Computer viruses are mysterious and grab our attention. Every time a new virus hits, it makes the news as it spreads quickly.

Viruses can do anything from annoying the user to deleting your entire computer. With more computers are being connected to the Internet, viruses are very easy to be spread.

While computers will never be 100% secure, there are many steps that you can take to prevent your computer from being infected with viruses.

What is a Computer Virus?

A computer virus is basically a malicious computer code that either harms computer data by writing over reserved areas of the operating system or attaches itself to other programs.

Viruses can infect computer files, programs, and write over parts of files. Viruses are also able to delete files from removable disk media (e.g. floppy diskettes, zip disks) or the hard drive.

More recent viruses take advantage of vulnerabilities in e-mail programs. These new viruses are written to not only damage your computer, but (with certain software configurations) also send a copy of the virus-contaminated document to all entries in the e-mail program's address book. Viruses can be transmitted through any platform - Macintosh, Windows, Linux, etc...

Viruses spread from computer system to computer system, usually by removable disk media, via e-mail and downloads.

Computers connected to a network are even more susceptible because newer viruses are written to spread through the network, infecting files on all connected computers.

While some viruses can be removed with antivirus programs, it is recommended that you keep two backup copies of your important files, thus increasing your chances to have a clean copy available in the event a virus infects a file.

Types of viruses

There are three basic types of ‘virus' each with a different intended purpose.

• True ‘viruses' bear the closest resemblance to their biological namesakes. Their purpose in life is twofold. Firstly, they want to multiply around the internet. Most commonly this is achieved by the virus sending itself to all contacts in your e-mail address book. Secondly a virus wants you to know it is there, so it starts to change files on your computer. This can result in a whole range of outcomes - from minor repairable damage to complete system failure.
• Worms are viruses, which seek only to proliferate around the internet with the intention of causing a system overload. This type of virus is typically used by groups of ‘hacktivists' who seek to make a social or political point by targeting a particular organization.
• Trojans are named after the Trojan Horse and are designed to reside on a host computer unseen, creating a security breach which another virus can exploit.

What is a Cookie?

You might have heard mention of ‘cookies' as a possible security threat. Cookies are used by many websites to keep information significant to a user. They are not a type of virus. It is not possible to pick up a virus from a cookie.

Cookies are commonly used for holding username and password information so that a website can remember you when you return to it. This would be the case when you perform online banking. Cookies are normally programmed to expire after a period of time.

Nonetheless, the power of cookies as a way of being able to collect personal information has not been lost on some of the more dishonest marketing companies that practice their various trades across the internet. ‘Spy cookies' as they have come to be known can reside on your system and collect data about you and your on-line buying habits.

Cookies are therefore a double edged sword. They are handy to save you having to remember passwords but can allow a lot more information to be gathered than you might want.

Your internet browser will have an option allowing you to decide whether to allow or disallow cookies. Some will even allow you to specify which sites you wish to allow and which to block. Always note never give away/out your personal particulars to a site or a person that you do not trust or are unsure of.

Antivirus Software

Most of the time, you will not know you have a virus until you scan for viruses. There are many options for scanning and curing viruses - free software, free online scans, downloadable trial versions of software, and software which you may purchase. (e.g. Norton Antivirus, AVG, McAfee etc...)

Virus software scans for viruses in real-time, which means that as your computer receives files, the software checks the files for viruses. The software will also constantly monitor the computer files to search for viruses.

It is vital when using a real-time virus scanner to updates frequently. By doing so, the software can detect all of the newly found viruses.

Below what to look out for in an Antivirus Software:

• Platform (operation system) Relevance: Most software packages are platform specific, meaning that software for a Windows 95 / 98 machine will not run on a computer using MacOS or Linux as its operating system
• ICSA Certification: The International Computer Sercurity Association has established accurate means for comparing antivirus detection rates. Only purchase software bearing the ICSA certification seal.
• Real-Time Background Protection: The software should not rely on your attention to do its job; rather, the software should detect viruses as soon as they appear in your system and alert you to this fact.
• Automatic or Scheduled Updates of Virus Definitions: This ensures that the software will detect and eliminate newly released viruses.
• Tech Support: Nearly all software companies offer online or telephone-based tech support. The number should be toll free, and offer useful tech support at no extra charge.
• Disaster Recovery: Many antivirus software packages will include a disaster recovery utility which allows you to recover lost or corrupted data and get your system "back to health" after a catastrophic virus attack.

Protect Against Computer Viruses

The most effective way of protecting your computer from viruses is to purchase reliable virus protection software (such as Norton Antivirus or McAfee etc...).

Other than virus protection, there are many less-obvious ways to protect your computer from viruses. Below is a list of Do's and Don'ts:

Do's

• Disable preview screens when using Eudora or Microsoft Outlook.
• Scan disks and zip disks before using them.
• Use a real-time scanner or frequently check your system with an online virus scanner.
• Update your virus scanner regularly.
• Backup important files regularly.
• Use personal firewall software to prevent unauthorized Internet access to and from your computer.
• Read the manual of your antivirus software.
• Most antivirus software are very complex, with dozens of settings. Reading the manual helps you get the most out of the antivirus software.
• If your computer suddenly begins performing strangely, you should run a virus scan on your entire computer.
• Be careful about disks from other computers. Not everyone uses virus protection, so if you are worried about a disk that you put into your computer, run a virus scan on it before you begin working on it.

Don'ts

• Never use disks from an untrustworthy source. Never download files from a site or a person that you do not trust.
• Never give away/out your personal particulars to a site or a person that you do not trust or are unsure of. Never open an email attachment that looks unusual or suspicious.
• Never open an email attachment from a person you do not know.
• Avoid pirated software.

Is your computer accessible someone other than you? If that is so, then be sure that they know about the tips noted in this article. Otherwise, you alone taking the precautions would not help protect your computer.

Many E-mail viruses are spread by sending itself to everyone in someone's address book. If the E-mail text does not sound like the sender, or you were not expecting the attachment, delete the message immediately.

If you have a Cable or DSL Internet connection, then your computer is a possible target of hackers. Be sure to purchase a firewall for your computer.

What If You Suspect Your Computer Is Infected

If you have reason to suspect your computer is infected with a virus (you have opened a suspicious email attachment, your computer is suddenly crashing or running slowly, you receive error messages whenever you start up your computer or try to launch an application), immediately disconnect your computer from the internet.

Next, check to see if your virus protection is up to date (the latest) and scan your hard drive for viruses.

If you use Microsoft Windows, Outlook, Outlook Express or Internet Explorer, it is very important to install the latest version upgrades and security patches from Microsoft.

Signs of a Possible Virus Infection

Your computer may be infected with a virus if:

• You have opened an email attachment from a person you do not know.
• You receive error messages whenever you start up our computer or try to launch an application.
• You have opened a file attachment to an email message which contains no personal information or does not mention the attachment.
• Your computer is crashing or running slowly.
• You have opened an e-mail attachment or another file whose name contains multiple extensions (e.g., resume.doc.lnk) or a .vbs or .pif extension (e.g., LOVE-LETTER-FOR-YOU.TXT.vbs).
• Unknown program windows appear and disappear after you start up your computer.

Glossary

boot sector virus

A boot sector virus infects the master startup files on a hard disk, or the startup files on a floppy disk. Boot sector viruses load into memory, tend to become more of a problem the more times the computer is started, and may prevent the computer from starting up at all.

macro virus

A macro virus exploits vulnerabilities in programs like Microsoft Word, Excel, and Outlook causing certain actions to perform automatically, usually triggered by selecting some other action in the program or when the program starts.

trojan horse

A Trojan horse is an attractive and seemingly harmless program, e.g., greatgame.exe that isn't a game at all, but contains a program that deletes all data on your hard drive.

virus

A computer virus is programmed to copy itself to reserved areas of the hard drive and from one file to another. A virus may spread rapidly or slowly, infecting programs and/or documents on a computer and attached drives. A virus usually spreads to other computers via a network, e-mail, and removable media, e.g., zip disks and floppy diskettes.

worm

While harmful as a virus, a worm is more insidious, in that it installs itself on computer hard drives it finds on a network. A worm can also spread via e-mail.

References http://www.computertim.com/howto/article.php?topic=general&idn=10  http://www.how-to.com/Operations/how_to_protect_against_computer_viruses.htm