User Guide

User’s Guide 63
Internet Security and Privacy
Biological viruses have proven to be tenacious— modern medicine’s success
in fighting viral infection has, so far, been rather limited. Fortunately, PC
viruses differ from biological viruses in that they are easier to combat, once
they are identified.
Are viruses really that dangerous?
Bear in mind that your chances of contracting a PC virus are slim, and even
more so, yourchancesof contractinga truly vicious virus . The scariest viruses
are malicious programs that intentionally corrupt or delete the data on your
PC. More benign viruses might simply display a message on your monitor or
make a strange sound, and then disappear. But even the most benign virus
occupiessome diskspace,andmanyremain inmemory,whichcancauseyour
PC to crash or behave erratically.
Types of viruses
There are three main types of viruses:
• File or progra m viruses: A program virus attaches itself to a specific
program on your PC. Since many PC’s share certain files in common (for
example,the DOSprogram command.com, or thecommand “dir”),which
make these files tempting targ ets forvirusprogram mers. Program viruses
are dormant until you run the associated program.
• Boot viruses (or Master Boot Record viruses): The boot sector of a disk is
aphysicallocationonthediskthatcontainsinformationaboutthediskand
the files it contains. All disks and drives have a boot sector, even if they
aren’t “bootable.” A boot virus infects the boot sector of floppy disks and
hard drives, and are activated w hen you access or boot from an afflicted
disk.
• Macro viruses: Macro viruses are contained in document files, such as
Microsoft Word or Excel files. These files can contain macros that can
automatey our work—butmacroscanalsobewritt entododamagetoyour
PC. Macro viruses are activated when you open an infected document file.
Afinalwordshouldbesaid abouthoax “viruses,”which are not virusesinthe
strictest sense of the term. A hoax virus replicates a hoax, spread by
misinformed (if well intentioned) e-mail claiming that if you download a
certainfile,orifyoureceiveane-mailwithacertainsubjectline,youwillinfect
your PC with a virus. E-mail messages are always safe; they are simple text
files, and cannot contain viruses. Attachments to e-mail messages (an
attachment is a file that a message sender attaches to a message—it is
downloaded to your PC when you retrieve the message) can contain viruses.
(If E-mail file access is turned on in Virus S entry, G uard Dog automatically
scans e-mail attachments before you open them.)