Information Technology Reference
In-Depth Information
the running of a virus could include its making one or more copies
of itself, perhaps inserting itself into new or existing files or sending
itself to other users or other computers. Thus, if a virus gets estab
lished anywhere in a computer, running it once may create many
additional copies—increasing the chance that it may be run again.
When a virus regenerates, it spreads.
Because any virus takes up space and utilizes CPU resources—at
least from time to time—any virus interferes with processing. If the
virus also modifies or deletes files, then it also may have destructive
effects.
The list of entry points for a virus, given in the previous section,
indicates that viruses may come to a computer in many ways: on an
infected disk, within an infected program, included in a data file
(e.g., a wordprocessing document or spreadsheet), as an email at
tachment, through a Web browser, or over the Internet. With so
many potential sources, and with sources arriving in a binary for
mat that is awkward for humans to read, it is impractical for a user
to physically scan every file that comes into a machine and expect
to weed out the viruses.
A user can, however, ask a utility program, called an
anti-virus
program
, to perform this scanning. Typically, an antivirus pro
gram contains information about known viruses, and compares
each file entering a computer against those known viruses. Thus,
when a new disk is placed into a computer, the antivirus program
immediately reads every file for signs that it might be a virus. Often
the computer is set up so that disk files cannot be accessed until this
virus scan takes place. If no viruses are found, then normal process
ing can continue. However, if a virus is identified, then either the
complete file will be deleted or the antivirus program will be in
structed to remove that virus program from the file (if such re
moval seems possible).
In this identification of viruses, note that the antivirus pro
grams normally compare new files with information about known
viruses. However, because various misguided folks create new
viruses regularly, the information for the antivirus programs must
