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Computer viruses implant instructions in other programs or storage devices, and can attack, scramble, or erase computer data. The danger of computer viruses lies in their ability to replicate themselves and spread from system to system. Few computing systems are immune to infection.

Email virus hoaxes

Email is also a primary means of propagating virus hoaxes. It's generally best not to pass on a virus warning unless you have confirmed its content with an authority on the subject. See:

High-risk behaviors

Email attachments are a common way transmitting viruses. Often a subject line will encourage you to open or execute an attached file, sometimes even under the pretext that it is a security patch. While executing an attachment is the most common way to become infected, it is possible, with certain feature-rich email clients (e.g., Outlook) and certain security settings, to launch a virus simply by opening or previewing an infected email message. Text-based clients (e.g., Pine) are much less susceptible to infection, though they can still receive and transmit viruses and viral attachments.

To reduce the potential for virus infection via email:

  • Do not open email attachments or other files from unknown people.
  • Be suspicious even of attachments you receive from people you know, and scan them with updated antivirus software before opening them.
  • Keep your computer's antivirus software up to date and active.

Instant messaging (IM) is also a common means of transmitting viruses to your computer. Be careful about following links that are sent to you via IM, and don't follow links that that come from unknown senders, or that install or run programs.

Many viruses and worms spread through file-sharing software. The best way to avoid viruses via file-sharing programs is to not install or use them to begin with. However, if you do use them, do not install free software that you find when using them.

Protecting against viruses

For tips on protecting your computer against viruses, see:

Viruses and antivirus software

For information about viruses and antivirus software, see: