A virus may also infect your system by downloading software off the Internet. For example, you get an e-mail message with a program attached to it. The message warns you about a virus and tricks you by stating the attached program is the antidote to the virus. You open your e-mail, run the antidote program and that sets the virus in motion. A virus may be distributed in any executable program.
Viruses usually make copies of themselves and attach themselves to other programs.
They may do anything from displaying annoying messages to corrupting your data to erasing your entire disk. Viruses are operating system specific, meaning that a virus that affects a Windows system will not hurt a Macintosh. There are many virus checking software packages. Some are free, and some you can buy. Most virus checkers can be run by hand or at periodic intervals.