How to avoid computer viruses
Types of computer virus
Combating the crime
What to do if you get a virus
A computer virus is a computer program that is written by a malicious author
They spread by copying themselves, then transferring on to other computers
There are around 53,000 computer viruses in existence, with a new one detected every 18 seconds
A computer virus can do anything from popping up a short message to wiping key files so your computer doesn't work
The "ILOVEYOU" virus infected up to 45 million computers, causing £7 billion worth of damage world-wide
How to avoid catching a virus
Dos and Don'ts
Stay calm. A computer virus isn't dangerous until the infected email is opened. Delete any mail you think is infected and empty your deleted items folder Don't open any attachment you are not sure about, even if you have a virus scanner
Read the email. Check that the contents of the message makes sense before you open any attachments
Don't forward any attachment to a friend without being sure it is safe
Look out for hoaxes. There are many emails warning of "the most destructive virus ever", but often these viruses don't exist Don't send an email about a "new virus" without checking it out. Visit sites like vmyths.com to check for hoaxes
Send any email you think is infected to an anti-virus company (you may have to own a copy of their virus software). They can tell you if it is a virus or not Don't send mail that may contain a virus to anyone other than official virus companies. Mail filtering systems will probably delete it anyway
Make sure you have a recent backup of your most important work Don't place backup floppy disks in your computer if you think you have a virus, as the virus could spread to your backups
If you get a computer virus you'll need to use a virus scanner to get rid of it Don't be blasť just because you have a virus scanner. You will still need to keep your eyes open in case a new virus emerges
There are many kinds of virus, all work in slightly different ways. Find out what types of virus are flying around the Internet.
What can you do if you get one? Read our survival guide.
Who would write a computer virus? Meet the hackers, crackers and script kiddies!
How Do Computer Viruses Work
Types of virus
From worms to macros, there's a whole host of viruses out there to catch...
These viruses spread via computer networks. The ILOVEYOU virus above was a classic example of a worm. These viruses are becoming an increasing threat as a growing number of computers are permanently connected to networks. Worms can spread over corporate networks or via emails sent over the Internet.
A Trojan virus takes its name from a story in Homer's Iliad where Greek soldiers pretended to make peace with their enemies, the Trojans. The Greeks made a grand peace-keeping gesture - the gift of a large wooden horse.
When the Trojans hauled it inside their city gates, a small band of Greek warriors leapt out. They opened the gates and let the rest of the Greek army storm in to capture the city.
A Trojan virus is one that opens your computer up to malicious intruders, allowing them to read your files.
A file virus is one that replaces a key system file on your computer. These viruses can reload themselves every time you start your computer up. Once they're in the memory, they can spread by writing themselves to any disk you insert into your disk drive.
Boot sector viruses
This is an early type of computer virus that spreads by hiding itself in an invisible location on your hard drive or floppy disk. When your computer reads an infected floppy disk, the virus is copied from the disk to your computer's memory.
From there, it writes itself to the 'boot sector' on your hard drive. The boot sector is read each time you turn your computer on. So the virus is constantly reloaded and can copy itself on to other floppy disks. These viruses are fairly rare nowadays, as they are easy to catch.
A macrovirus infects word processor files, such as Microsoft Word documents. Although not as dangerous as other viruses, they can spread quickly if a Word file is sent via email. After an initial scare, Microsoft added protection into later versions of Word, so you receive a warning about infected documents.
The virus hoax came about after friends sent each other emails about a new virus threat. Someone decided that they could cause just as much trouble by sending out fake warnings rather than real viruses.
Hoaxes may seem harmless, but they do a great deal of damage to the Internet as a whole. Not only do they slow down traffic and clog up email servers, but they also cause people to panic. Companies can spend money and time investigating what is just someone's idea of a joke.
Mobile phone viruses
Although rare, mobile phones are the latest technology to be hit by virus problems. Some people have discovered that it is possible to crash certain types of mobile by sending them a coded text message.
Mobile phones can now be affected by viruses
Mobile phone viruses
A recent case in Spain started via email. When the user opens the attachment on their PC, the virus generates a "junk" text message (using a Spanish telecommunications company website) which is sent out to a random phone number. Anti-virus software companies say that the virus will not infect the mobile phone itself.
Who Writes Computer Viruses?
Virus authors are normally 14-26 year old males who spend a lot of time on their computers. Some of them want to prove they are good programmers. Others want to show that they have the power to cause large-scale problems.
But most viruses don't constitute good programming, as many fail to deliver their payload. Many are re-hashed versions of old programs that require little skill to produce.
In the UK, if you're caught using a computer for criminal reasons you can receive a five-year sentence and an unlimited fine. If convicted of 'cyber-terrorism', then you can be given the same sentence as a terrorist bomber.
How do you catch a virus writer?
Although the Internet allows computer viruses to spread quickly, it also helps to catch the authors.
Each computer connected to the Internet has an address, similar to a phone number. This is called an IP address and looks like this: 184.108.40.206. Every email you send is marked with your IP address and this information is hard to remove.
Unique IP adresses are used to locate hackers
Your IP address reveals what company (or Internet Service Provider) holds your account. The company can then find out which customer sent the mail. So if you send a virus to a Member of Parliament, it won't be long before the police are knocking on your door asking questions.
Sophisticated virus authors would be able to cover their tracks to some degree, but there is usually some way to track them down.
Hackers, crackers and script kiddies
There's a whole zoo of cantankerous coders out there:
# Hackers: people who try to find security flaws in corporate computer programs. Most hackers don't aim to cause problems, but they might send an anonymous email to the person in charge warning them of their security problem. Amongst other hackers, there is much honour to be gained by those who can 'crack the uncrackable' programs
# Crackers: unlike hackers, crackers are less sophisticated. They like to break into people's websites and replace their corporate homepage either with pornographic images or hoax messages
# Script kiddies: young virus pirates, who copy old computer viruses and modify them. Often they don't work. If they do, they are seldom as dangerous as the originals and can be easily destroyed
What To Do If You Get A Virus
Even if you are careful to avoid a computer virus, you may still be unlucky. If you are you'll need to get a piece of software called a virus scanner. Many people put off getting a decent virus scanner because it costs too much, or they think they won't get a virus.
They cost around £40 from most good computer stores. This will include a certain amount of updates and technical support for a year. Updates after this period can be obtained at fairly low cost.
It may seem like an extra unnecessary outlay, but if you are running a small business from your home computer then you need to protect your work. Backups can help, but if you put your work back on a machine with a virus it will just get infected again.
How do they do that?
Before you go and spend hard earned cash on a virus scanner it is worth understanding what they do.
A typical virus scanner will have two main functions:
# scan for new viruses entering your computer
# clean up any viruses it finds and make sure they can't do any more harm
Virus scanners are pieces of software that run all the time. So when you start up your computer the virus scanner will also start. This ensures that viruses are caught as soon as possible. A virus scanner will also check the following for viruses:
# disks inserted in your PC
# email you receive
# programs you download from the Internet
If you have already got a computer virus, the software will find these and:
# Notify you that you have a virus (stay calm!)
# Try to repair the file the virus has infected
# Isolate any files that can't be repaired
The virus scanner will always try to rescue any files it can. There are some viruses that don't destroy files, instead they 'corrupt' them so they cannot be used. Good virus scanners can often reverse this.
If the scanner cannot repair a file, it will place it in a secure area so you can't run it by accident. Then you can send the virus to an anti-virus company. If it is a new one they will add it to their database and at least you will be able to help prevent other people catching it.
Online virus scanners
If you don't yet have a virus scanner but think you might have a virus then try using an online virus scanner. These pieces of software work by sending you a small program over the internet. From there you can find out if you really do have a virus. If you do then now is the time to purchase some anti-virus software.