Understanding Viruses
FAQs | Glossary Of Terms | How-To Articles
The first tenet of warfare is this: know thy
enemy. So what exactly are computer viruses? Computer
viruses are devious little computer programs that
attach themselves to legitimate program hosts
and then engage in rampant self-replication. It's
easy to be fooled by their small size. Don't be.
They're never small for long. Computer viruses
propagate like rabbits ó and by the time you first
recognize their presence, your data may be permanently
damaged or erased.
On this point, however, an important clarification
must be made. Like biological viruses, computer
viruses are not inherently destructive. You're
probably harboring a fugitive cold virus in your
body right now, even if you're not actually sick.
With both biological and computer viruses, you
can be infected without being affected. Your computer
can be a veritable hive of viruses without exhibiting
any visible symptoms or actual damage. If not
instructed to do otherwise, viruses will quietly,
unobtrusively and perpetually replicate. They're
only destructive if intentionally engineered to
be so.
Malicious computer viruses contain a "payload"
ó a programming element separate from the self-replication
code that executes its objectives. For example,
a payload might display a personalized message
on your monitor. It might erase critical data
or program files, reformat your hard drive, or
infiltrate your messaging software and overload
the local network with authorless e-mail. But
not all computer viruses are created equal. Some
are full of sound and fury, yet signify nothing.
Others are silent but deadly. In general, though,
computer viruses are of three main types:
Macro Viruses: These are the most prevalent
type of virus today. Unlike conventional viruses
which can attach to virtually any program, macro
viruses prey on specific programs. A macro itself
is an instruction code that automatically executes
other program commands. Many popular and prominent
software applications utilize macros extensively.
Essentially, macro viruses are macros that embed
within a program and self-replicate.
Macro viruses that run on Microsoft applications
like Word and Excel are particularly common ó
chiefly because certain programming strategies
employed by these applications make them particularly
susceptible. Macro viruses work like this: when
an infected document is initially opened, the
macro virus embeds itself in the associated application
and then proceeds to attach itself to every subsequent
document created. In this way, the macro virus
is unwittingly disseminated whenever the user
transfers a document.
Parasitic Viruses: These are the most infectious
type of virus. Parasitic viruses attach themselves
to executable programs like .com or .exe files.
Once an infected file is launched, the virus is
free to replicate itself, embed in primary memory,
or release its payload. Further, it can corrupt
not just specific programs, but virtually any
program being processed in RAM.
Boot Sector Viruses: The boot sector is essential
software that resides on hard, floppy or optical
disk, and is responsible for loading your operating
system into memory at the start of a computing
session. Boot sector viruses penetrate this vital
boot sector and alter its contents. As opposed
to macro viruses, boot sector viruses are spread
not by sharing documents, but diskettes. Whenever
new diskettes are introduced to a previously infected
computer, the boot sector virus is transferred
to the healthy diskette, which then conveys the
virus to other computers, and so on.
These are all considered true computer viruses.
Another commonly observed form of computer pestilence
(though not literally a virus) is the worm. Worms
differ from viruses in that they do not require
a host to wreak their havoc. Other viruses are
referred to as Trojan Horses. Trojan Horses are
viruses that masquerade as legitimate programs,
documents or other software, only to reveal their
true function later. Trojan Horse viruses are
often spread through e-mail or online bulletin
boards.
Certainly no one would knowingly expose their
computer to a virus. Unknowingly, however, thousands
daily place their machines in peril. Ignorance
is no excuse, though ó an ounce of prevention
is worth a pound of cure. The following are some
common troubleshooting techniques for keeping
your computer virus-free:
- Always rely on a reputable anti-virus software
application like Norton or McAfee.
- Always scan new files, diskettes or software
before loading them on your machine.
- Always back-up critical software or files
to avoid permanent loss due to infection or
deletion.
- Always be wary of strange operating tics
or unusual graphics.
- Always ensure vigilance from the other members
on your computer or network.
- Always write-protect your system and program
disks.
- Always enable Macro Virus Protection in all
Microsoft applications.
- Never share diskettes or software without
assuring their integrity.
- Never download e-mail or Internet files/programs
without scanning them first.
- Never act on an e-mail virus alert without
confirmation from an IT professional or trustworthy
resource.
- Never boot your system with a diskette other
than the original.
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