What is a computer virus?

Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.

A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.

Viruses are often spread by attachments in e-mail messages or instant messaging messages. That is why it is essential that you never open e-mail attachments unless you know who it's from and you are expecting it.

Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files.

Viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.

What is a computer worm?

A computer worm is a self-replicating computer program. It uses a network to send copies of itself to other nodes (computers on the network) and it may do so without any user intervention.

What is a Trojan horse?

A Trojan horse is destructive program that masquerades as a benign application. Unlike viruses, Trojan horses do not replicate themselves, but they can be just as destructive.

Infection Methods:

• Removable media.
  • Whenever you use removable storage your computer is at risk to be infected by a virus.
• The Internet.
  • Downloads from the internet especially from suspicious site; and from email attachments.

Virus Infection Symptoms:

The symptoms of virus infection will vary depending on the virus. These may include:

• Screen display problems.
• Computer doesn't boot, or takes a long time to boot.
• System hangs up.
• Unusually frequent disk activity.
• Files deleted or destroyed.
• Hard disk corruption.

Checklist: Protecting your computer from viruses:

• Ensure you have installed the most recent Anti-Virus software. Check the vendor's Web site regularly for updates.
• Always back up your data. If a virus infects your computer, you may need to rebuild your data from these backups.
• If you believe you have been exposed to a virus, and notice any of the above symptoms, run your Anti-Virus software immediately.
• Always scan your email attachments with Anti-Virus software before opening them. Pay particular attention to Executable files (i.e., files with a .exe file extension), Microsoft Word and Microsoft Excel files.
• When you open a Microsoft Word or Microsoft Excel file that contains Macros, you will be asked 'Do you want to disable Macros?' In most instances, you should select 'Yes'.
• If you share a computer, have an agreed protocol with other users that covers caution when using external media, and regular Anti-Virus scanning.
• Only download software from Web sites you trust. Even then, it is wise to check for viruses.

Checklist: What to do if you are infected:

• If you don’t know very much about the computers or virus, seek help from someone knowledgeable in these areas. It is good to be part of a local support group (such as AWORC), where people can provide advice or assistance if the situation should arise.
• If you are familiar with the Vaccination function of Anti-Virus software, kill the virus and check all external disks so infection will not happen again.
• If you share a computer or are connected to a local area network, notify other users about the virus in order to raise awareness and take preventative action.