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Fighting a virus

Electronic antibiotics for your computer's infection

Despite careful planning, it is possible to fall victim to a virus. This could be for any number of reasons. Perhaps your anti-virus software was for some reason disabled, or maybe the virus was inadvertently downloaded from the Internet.

Whatever the reason, watch out for the following signs that can warn you of infection:

Increased email activity on your network, especially messages with identical or unusual subject headings.

Your computer has less available memory than it should.

It inexplicably shuts down at certain times.

Some of your files are corrupt or don't work as they should.

Some of your files or programs are missing.

Unknown files or programs appear on your computer.

If you have a network, disconnect the suspected computer immediately.

Don't panic. Use your anti-virus software to double-check that you're infected. Sometimes a system can appear to be infected when it's not. For example, false alarms happen if you run two anti-virus software packages at the same time, something to avoid. There are also joke programs that convincingly emulate virus symptoms.

Once you've confirmed that you have a virus make sure that everyone knows about it and checks their systems for symptoms. Inform them of what they can do to stop or minimise further spread of the infection. Give instructions regarding what to do about the infected machines.

To be safe contact everyone - without using email - that you you recently exchanged files with and let them know that they stand a chance of infection.

First of all, determine the extent of the infection with a full virus scan.

Make sure the malicious code isn't in memory before trying to remove it. To start the system without the virus in memory, exit all open programs and reboot the computer with an uninfected emergency boot floppy inserted in the A: drive.

Once you know which type of malicious code you're dealing with, use your anti-virus software to disinfect your system.

Some viruses and worms are sticky customers and cannot be removed automatically, so use a clean computer to check your software vendor's site for instructions about manually removing any final traces.

If you can find an infected file before it's opened and has a chance to spread through your system and network, delete it

Strange messages pop up on your monitor.

Music and sounds play spontaneously.

Because viruses, worms and Trojan Horses each infect different parts of the system, it's impossible to devise a cure-all for treating infection. There are, however, procedures that you can follow to clean up your systems and restore your data.

Regular back-ups are an essential part of your anti-virus arsenal. If any of your data is lost or damaged beyond repair, these may be your only hope of recovering your work.

It's also a good idea to develop a collection of read-only disks containing the free tools distributed by many anti-virus developers.

Make sure your employees know what to look out for and will inform you of any virus symptoms they notice.

Contain the outbreak as quickly as possible. ing it may be enough to avoid further problems. This is especially the case if your anti-virus software flags an infected email attachment, as you need to open it to become infected.

As a last resort you may need to reformat

By reformatting your drive you destroy all your existing data and will need to reinstall all your files and software to get up and running again.

After you reformat your drive reinstall your anti-virus software first, so that you can test your software and back-ups before you install them.

Your anti-virus software will often be able to repair files with minor damage. However, you will have to restore badly damaged or destroyed files and programs from your back-up copies and installation disks. You may also have to replace some files from your original system installation disk.

Viruses and worms self-replicate, so make sure that you've found and deleted all copies. Once you've disinfected the computer, check that all trace of the malicious code has been removed with another virus scan. Only reconnect it to the network once you're confident that the computer is clean.

Once the dust settles it's time to review your preventative measures. Somewhere, somehow the malicious code slipped in. Establish how this happened, and review your virus defences to see how they can be improved to avoid future incursions.

Find out how to protect your business with anti virus software

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What next?

Our security guide contains lots of practical information about dealing with virus and spyware infections. You can download or order it free of charge.

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