Computer viruses, spyware and adware

A computer virus is a program that spreads by making copies of itself, just like a real virus. Most have a destructive "payload" that is activated under certain conditions. Viruses cause varying amounts of damage.

Spyware gathers information about a user's Internet activities, usually without the user's knowledge or consent. This is generally used for advertising. At its worst, spyware can take partial control of a computer and collect sensitive information like passwords.

Adware displays unwanted pop-up ads. Like spyware, it is typically installed with free software and pays the developer's costs. Adware is generally not dangerous, but can be very annoying.

Compared with Windows, MacOS and Unix computers are far less vulnerable to viruses because they have better security and fewer viruses target them.

How do you know if your machine is infected?

• Erratic behaviour
• Unexpected slowdowns
• Home page on Internet browser changing by itself
• Advertising on the screen that is unrelated to a specific Web page
• "Blackmail" or malicious messages
• Catastrophic loss of data

Preventing infection on Windows computers

These strategies will prevent most problems:

• Never double-click an unknown e-mail attachment that contains an executable file.
  These have extentions like .exe, .com, .vbs, .pif or .bat
• Create a separate "administrator" account, then turn off "administrator privileges" on your usual account
• Install antivirus software and ensure it is automatically updated online

Other good preventive measures:

• Avoid programs from unknown sources and stick to commercial software
• Limit access to your computers by other users
• Avoid macros. Enable Macro virus protection in all Microsoft applications

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