Computer viruses infect a computer in three basic ways: when a user (1) opens an infected file, (2) runs an infected program, or (3) powers on the computer with an infected disk in a disk drive. Today, the most common way a computer becomes infected with a virus is when a user opens an infected e-mail attachment.c
Methods that guarantee a computer or network is totally safe from computer viruses simply do not exist. Users can take several precautions, however, to protect their home and work computers from viruses. The following paragraphs discuss a variety of precautionary measures designed to protect computers from viruses.
Do not start a computer with a floppy disk in drive A - unless you are certain the disk is an uninfected boot disk. All floppy disks contain a boot sector. During the startup process, the computer attempts to execute the boot sector on a disk in drive A.
Even if the attempt is not successful, a virus on the floppy disk's boot sector can infect the hard disk on a computer.
Never open an e-mail message attachment unless you are expecting the attachment and the e-mail message is from a trusted source. A trusted source is a company or person you believe will not send a virus-infected file knowingly. If the e-mail message is not from a trusted source, delete the message immediately. Do not open or execute any of its attachments.
Many e-mail programs enable users to preview, or look at the contents of, a message before or without opening it. Some viruses can infect a computer when a user previews an e-mail message. Thus, users should turn off message preview in their e-mail programs.
Some viruses are hidden in macros, which are instructions saved in an application such as a word processing or...