Trojan Horses are closely related to computer viruses, but
they differ in that they do not attempt to replicate themselves.
More specifically, a Trojan Horse performs some undesired --
yet intended -- action while, or in addition to, pretending to
do something else. A common example is a fake login program,
which collects account information and passwords by asking for
this info just like a normal login program does.
Many computer viruses are malicious -- in other words, they
can erase your files or lock up whole computer systems. Other computer
viruses are more benign -- they don't do any direct damage other
than by spreading themselves locally or throughout the Internet.
Regardless, computer viruses should always be treated.
More general information about computer viruses:
TJU Computer Virus Information Page:
==> http://www.tju.edu/tju/dis/virus
2.
What Kind of Damage Can Computer Viruses Do?
The damage a computer virus
can inflict on your system depends on many things, including
how sophisticated the virus is. Here is a short listing of the
types of damage viruses can do to your computer -- they can really
hit you where it hurts:
- Some viruses can delete or change files.
Some viruses will delete all of your documents, or even reformat
your hard drive, making your computer unusable.
- Some viruses can release confidential
information like credit card information, account numbers,
and passwords by emailing it to random email addresses or the
address of the virus writer.
- Some viruses
can slow down your system dramatically.
- Some viruses plant monitoring software
or change security settings that allow hackers to enter your
computer without you knowing about it and steal information
or control it.
Other viruses, like Internet worms can have
widespread effects on computer networks and the Internet.
3.
Your
Computer May Have a Computer Virus If..
How do you know if you
have a computer virus? If you're not running an antivirus program
(see the next section), you may not know at all since many viruses
are benign.
Some symptoms of a virus infection are:
- Your computer displays strange messages,
plays music, or shows odd graphic displays.
- Your computer takes longer to boot
up, operates more slowly than usual, and takes longer to
start programs.
- Your computer has much less memory
or hard drive space available.
Some legitimate software can cause these symptoms,
so *the only way you can be sure your computer is virus-free
is to regularly scan it for viruses using antivirus software*.
4. How
Can You Protect Your Computer From Viruses?
As we've indicated, you
need antivirus software to be safe. You should consider the cost
of the software as part of the purchase of your computer -- it's
that important.
Once you've installed the antivirus software,
you will need to download regular updates that tells the antivirus
software about new viruses and how to detect them. Most antivirus
software comes with a year's worth of updates, and you can usually
set the software to either automatically download the updates,
or display a reminder for you to do so.
This is vital since there are over 500 new viruses
discovered each month!
Norton AntiVirus and McAfee VirusScan are the
two best-known antivirus programs for the Microsoft Windows operating
systems. For Macintosh users, Norton AntiVirus and McAfee's Virex
for Macintosh provide protection. For Linux users, try RAV AntiVirus.
While the vast majority of viruses are written
to infect Windows-based systems, Macintosh and Linux users should
still also have virus protection.
All antivirus software lets you scan the computer's
memory and hard drive for viruses. Depending on the software
package, the antivirus program may also be able to protect against:
- Incoming emails and email attachments
with viruses.
- Viruses received through instant messaging,
such as ICQ.
- Infected downloaded files, before you
open the file.
- Attacks against your computer from outside
(firewall software).
If you are strapped for cash, AVG Anti-Virus
provides a free version of its antivirus program and free updates
for Windows-based computers. And if you just want to scan your
computer for viruses for free *right now*, check out Trend Micro's
free online virus scan and McAfee FreeScan.
More information about antivirus software:
Norton AntiVirus
==> http://www.symantec.com/nav/
McAfee VirusScan
==> http://www.mcafee.com/myapps/antivirus.asp
Virex for Macintosh
==> http://www.mcafeeb2b.com/products/virex/default.asp
RAV Anti-Virus (Linux)
==> http://www.ravantivirus.com/
AVG Anti-Virus (free version available!):
==> http://www.grisoft.com/
Trend Micro's free online virus scan (requires
Internet Explorer version 4.0 or later or Netscape version 3.01
or later):
==> http://housecall.antivirus.com/housecall/start_corp.asp
McAfee's FreeScan (requires Microsoft Windows
and IE 5.0 or
later):
==> http://www.mcafee.com/myapps/mfs/default.asp
5.
How Can Your Computer Catch a Virus?
There are only two ways
for your computer to get a virus:
- You load the virus onto your computer through an infected
floppy, CD-ROM, or other storage medium.
- The virus arrives by a downloaded file, email attachment,
or other method from the Internet or a network.
At this point, an infected file is on your computer's
hard drive. But remember, your computer will only become infected
if you launch or view the file, or run the infected program.
So an important tip is to always scan new files
for viruses before you use them.
Take these precautions when working with files
and the
Internet:
- Before you load a file or install software
onto your computer from a floppy disk or CD-ROM, use your
antivirus program to scan the floppy or CD.
- If you receive an email attachment
from an unfamiliar email address, or an attachment you were
not expecting, either scan it or delete it (preferred).
- If you receive an email attachment
from someone you know, and your antivirus program does not
automatically scan incoming emails, save the attachment to
your hard drive and scan it with the antivirus program. Your
friend or colleague's computer may be infected with a virus.
- When you download software from the
Internet, be sure to download it from the software company's
site or a recognized download site ( http://downloads-zdnet.com.com/
, http://www.download.com or http://www.tucows.com for example).
Download the file to your hard drive and scan it using your
antivirus program before you run or decompress it.
- If someone sends you a 'joke' file
or electronic greeting card that you must launch to view,
be very wary.
- If possible, don't use Outlook or Outlook
Express as your email program. More viruses are spread from
the security
holes in Outlook than any other email program.
Many experts now feel that the dangers of being
infected by a virus are so great that it just isn't worth receiving
email attachments. You can set your email program to stop accepting
them.
More virus prevention tips are available at:
==> http://www.mcafee.com/anti-virus/virus_tips.asp
News about the latest virus threats are available
at:
==> http://www.symantec.com/avcenter/
==> http://www.mcafee.com/anti-virus/default.asp
6. When
a Virus Isn't a Virus: Hoaxes and Chain Emails
Every day, we receive forwarded
emails from concerned readers or friends telling us about a new,
super-dangerous virus that's unlike anything the Internet has
seen before.
Unfortunately, 99% of the time, these forwarded
emails are hoaxes.
In fact, most real viruses don't come with email
alerts (except from your antivirus software company), whereas
almost all these other virus emails are hoaxes.
Much like urban legends, these hoaxes get sent
around because they sound so real. But like chain letters, you
can stop the hoaxes at the source. Just research the following
sites, make sure the email is a hoax, and then delete it.
More information about virus hoaxes:
HOAXBUSTERS Home Page
==> http://hoaxbusters.ciac.org/
Symantec Security Response - Hoax Page:
==> http://securityresponse.symantec.com/avcenter/hoax.html
VMyths.com
==> http://www.vmyths.com/
Urban Legends Reference Pages: Computers (Viruses):
==> http://www.snopes.com/computer/virus/virus.htm