1. What is a computer virus?
A computer virus is a program designed
to spread itself by first infecting executable files or the system
areas of hard and floppy disks and then making copies of itself. Viruses
usually operate without the knowledge or desire of the computer user.
2. What are worms, macro viruses
Some people distinguish between general
viruses and worms. The "worm" acquired its name because
of the way it gradually infects a system, much like a worm eating
it' way through an apple. Most worms will try to infect as many computer
files as possible, including free space. Other worms duplicate by
attaching themselves to e-mail, or other file transfers.
A macro virus is embedded in a document instead of a program. Documents
created in programs like Microsoft Word and Microsoft Excel can be
infected with macro viruses.
A Trojan Horse is a destructive program that pretends to be a useful
one. Most Internet-acquired viruses are initially dropped by Trojans.
The Trojan contains the virus code or program, which then infects
your computer. So, although the Trojan itself might not be self-replicating,
the virus it contains is.
3. How do viruses spread?
When you execute infected program code,
the virus code will run and attempt to infect other programs, either
on the same computer or on other computers connected over a network.
The newly infected programs will then try to infect yet more programs,
and the pattern repeats itself.
When you share a copy of an infected file with other computer users,
running the file may also infect their computers; and files from those
computers may spread the infection to yet more computers.
If your computer is infected with a boot sector virus, the virus tries
to write copies of itself to the system areas of floppy disks and
hard disks. Then the infected floppy disks may infect other computers
that boot from them, and the virus copy on the hard disk will try
to infect still more
4. What do viruses do to computers?
Viruses are software programs, the actual
effect of any particular virus depends on how it was programmed by
the person who wrote the virus.
Some viruses are deliberately designed to damage files or otherwise
interfere with your computer's operation, while others don't do anything
but try to spread themselves around. But even the ones that just spread
themselves are harmful, since they damage files and may cause other
problems in the process of spreading. Note that viruses can't do any
damage to hardware: Warnings about viruses that will physically destroy
your computer are usually hoaxes, not legitimate virus warnings.
5. What about viruses in E-mail?
You can't get a virus just by reading
a plain-text E-mail message or Usenet post. What you have to watch
out for are encoded messages containing embedded executable code (i.e.,
file attachment (i.e., an encoded program file or a Word document
containing macros). In order to activate a virus or Trojan horse program,
your computer has to execute some type of code. This could be a program
attached to an E-mail, a Word document you downloaded from the Internet,
or something received on a floppy disk. There's no special hazard
in files attached to Usenet posts or E-mail messages: they're no more
dangerous than any other file.
6. Some general tips on avoiding virus infections:
Install anti-virus software from a well-known, reputable
company. Update it regularly, and use it regularly. New viruses come
out every single day; an anti virus program that hasn't been updated
for several months will not provide much protection against current
In addition to scanning for viruses on a regular basis,
install an 'on access' scanner (included in most good anti-virus software
packages) and configure it to start automatically each time you boot
your system. This will protect your system by checking for viruses
each time your computer accesses an executable file.
Virus scan any new programs or other files that may
contain executable code before you run or open them, no matter where
they come from.
Anti-virus programs aren't very good at detecting Trojan
horse programs, so be extremely careful about opening binary files
and Word/Excel documents from unknown or 'dubious' sources. This includes
posts in binary newsgroups, downloads from web/ftp sites that aren't
well-known or don't have a good reputation, and executable files unexpectedly
received as attachments to E-mail or during an on-line chat session.
If your E-mail or news software has the ability to
code contained in or attached to a message, it strongly recommend
that you disable this feature.
Be extremely careful about accepting programs or other
files during on-line chat sessions.
Do regular backups. Some viruses and Trojan horse
programs will erase or corrupt files on your hard drive and a recent
backup may be the only way to recover your data.
7. I think my computer might have a virus; what should
The safest way to ensure that your computer
is virus free is to install a virus scanner with the most recent virus
definition files. The ACS has a license for the free installation
of Norton anti-virus, and MacAfee for PCs, and Macintosh. The license
encompasses a free copy to all faculty, students and staff. For more
information visit the ACS site. It is also imperative that you periodically
check for updates for the anti-virus programs on their sites, or through
the ACS site. In addition the ACS provides technical support, if you
are not able to remove the virus. ACS technical support (http://acs.aucegypt.edu/techsupp.html)