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| BILL THOMPSON'S GUIDE TO COMPUTER VIRUSES |
 Bill Thompson is a technology analyst and commentator for BBC News Online
Listen again to Computer Virus Scares
It might seem impossible to avoid getting a computer virus on your home PC, but with a little care you can keep these nasty programs away from your valuable files.
What is a Virus?
A virus is a special sort of computer program that can hide itself inside another program or in a file on your computer. A program or file with a virus is ‘infected’, just like your cells can be infected with ‘flu virus. When an infected program is run or an infected file is read, the virus program runs instead. Sometimes you can tell a virus is running, but often the virus is unobtrusive and you will not notice it. A virus is not the same as a ‘worm’. A worm is a program that spreads from computer to computer, but it does not hide itself inside other programs or files. However the effect of having a worm is often the same as a virus, so few people bother to distinguish between them. Anti-virus programs and firewalls will block worms and viruses.
What do Viruses do?
A virus can do anything on your computer that any other program can do, including reading your files, changing or deleting information, and accessing the internet. Some viruses simply spread themselves around as many computers as possible, but most also do something else. This is called the ‘payload'. Lots of viruses run a program which lets the virus writer get access to the infected computer over the internet, so that they can steal information, wipe files or even install hidden programs. This is called a ‘backdoor’ or a ‘trojan’, after the Trojan Horse which let Greek solders sneak into Troy. Others change or destroy your documents, or steal files which might contain passwords, bank account details or other secrets. A common trick is for a virus to install a ‘key logging’ program. This keeps a record of everything that the computer’s owner types, including bank passwords and other sensitive information. Any information found or recorded by the virus can be sent to the virus writer.
How do Viruses Spread?
Before the internet became popular viruses spread on floppy disks or other sorts of computer data storage, like Zip disks. Inside large organisations they could also spread over the internal computer network. Now most viruses spread over the internet. Some will spread directly, searching for computers which are unprotected or are running programs with security holes. Most, however, use email to get around. A virus program will send a fake email message that looks like it comes from the owner of the computer it has just infected, and it will put a copy of itself into an attachment. When a recipient opens this attachment, the virus runs and infects a new computer. A single virus program can send out thousands of emails an hour, spreading rapidly around the net.
How Can I Protect Myself?
Before a virus can infect your computer it has to get to it. A ‘firewall’ program constantly monitors your internet connection looking for trouble. It will stop viruses copying themselves to your computer. If you have a virus, your firewall can also stop it sending your private information out over the internet. Anti-virus software will examine all emails and other files that you copy from the internet and spot most viruses. It can also look at every file on your hard drive to see if they are infected. New viruses are created all the time, and some old viruses change frequently to try to defeat the anti-virus programs. You’ll need to keep your list of viruses to look out for up-to-date, and you will probably have to pay an annual subscription for this.
Good sense helps a lot. Viruses often send themselves out as email messages with attached files – the attachment has been infected. If you receive an email with an attachment, even from someone you know, don’t open it unless you are absolutely sure that it is safe. A virus program can create fake emails that look like they came from someone you know. It is always safer to send an email back asking Anne if she really sent you a file!
Will There Always be Viruses?
It seems likely that there will always be malicious programs out there, and some will spread from computer to computer like viruses do today. However work by companies like Microsoft on improved computer security may well reduce the number of computers that get infected to the point where virus writers simply don’t bother any more.We will also benefit from better anti-virus programs, firewalls on every internet-connected computer, and broadband always-on connections so that new virus alerts and program patches can be sent out as soon as a virus is found.
Top Tips
Get an anti-virus program for your computer, and make sure it is properly installed and working.
Download new anti-virus definitions every day. If you have a broadband connection, you can get this to happen automatically.
Use a firewall for added protection.
Keep your computer programs up to date so that viruses can’t use well-known security problems. Install patches regularly.
Don’t open any attachments in email that you weren’t expecting to receive, even if the message is from someone you know. - You can always ask someone to confirm that they’ve just sent you something.
If you think you’ve got a virus, disconnect your computer from the internet before you carry out any checks. Then you won’t be spreading the infection to other people or sending out hundreds of fake emails.
Jargon
virus: a program which can infect other programs or files and make copies of itself
worm: a program which can make copies of itself
trojan: a program which lets other people use your computer without you knowing
backdoor: same as a trojan
email spoofing: a way of making fake emails that look like they came from a real person
firewall: a program that monitors your internet connection looking for danger
infection: having a virus having virus-containing files on your computer
attachment: a file that is sent along with an email message
patch: a modified version of a program or part of a program that fixes a problem
payload: what a virus does apart from spreading itself and infecting files and programs
And Finally
Despite the many problems and dangers which owning and running an Internet-connected home computer can bring, the benefits are also great. As with so much else in life, the trick is to get the balance right. If you are careful about the emails you read and use an anti-virus program and a firewall then you’ll find using the internet is both safe and rewarding.
Where Else to Go
BBC WebWise website
BBC News Online regularly reports on new viruses and what you can do to protect yourself. See an example here.
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