small programs that are executed when a computer boots up. In the
past, boot sector viruses were spread mainly by infected bootable
floppy disks. Today, any disk can cause infection if it is in the
drive when the computer boots up, through a network and/or by email
attachments. This type of virus is extremely dangerous since the Booth
Sector Virus executes every time a computer starts up. Another type
of virus, called a multipartite virus, is capable of infecting both
files and the boot sectors.
Are designed to infect specific types of executable
files that end in "EXE" or "COM". The virus is
program to overwrite a portion of the specific file with the viral
code. When the program is in run mode the viral code is executed and
may infect the software and transmit the virus to other files.
Have become widespread in recent years. A macro virus is a type of
computer virus that is encoded as a macro embedded in a document.
Many applications use macros, including popular spreadsheet and word
processing programs. Once a macro virus gets onto your machine, it
can embed itself in all future documents you create with the application.
If a copy of an infected file is transmitted to another computer by
e-mail or floppy disk, the virus can spread to the recipient's computer.
A good example of this virus was the " I Love You" virus.
Are viruses designed to attack an antivirus
program and thereby avoid detection. The way it does this is by stopping
virus definitions updates (Live Updates).
It's important to realize that viruses can't infect
email messages or Web pages, since these are both based solely on
text, and plain text cannot contain computer viruses. The two ways
viruses are most commonly spread are through e-mail attachments
and by floppy disk.
viruses designed to hide it's presence from traditional detection
techniques in the 'System Sector', which is the area of your hard
drive containing the programs used to start your pc. This type of
virus is able to go undected for years.
term "virus" is often mistakenly used to describe other
types of malicious programs or files. Here are some virus-like threats
that you should be aware of. In the past, boot sector viruses were
spread mainly by infected bootable floppy disks. Today any disk can
cause infection if it is in the drive when the computer boots up.
Boot sector viruses can also be spread across a network and by e-mail
attachments. These viruses usually remain active on your computer,
and can infect any floppy disk you access.
Programs: Like the construct from ancient
Greece, these programs use a disguise to gain entry to your computer's
applications. Trojan programs appear to be useful programs, but actually
contain an entirely different (and often harmful) program. For example,
you might download what you think is a video game, but when you attempt
to run the game it actually deletes critical system files. Trojan
horses are also common vehicles for remote administration programs
that let hackers control your computer. As with viruses, simply downloading
a Trojan program will not activate any harmful consequences; the program
must be run for it to take effect.
Unlike viruses, a worm is a self-replicating
program that doesn't infect other programs (although worms can be
used to transport viruses). Instead, a worm creates copies of itself,
which then create more copies. The explosive growth of the worm can
cripple networks by clogging data traffic with worm-related activity.
Be careful with hoax e-mails, this is the type
that contains false claims about devastating new viruses. Frequently,
these e-mails will instruct you to search for and delete a system
file, claiming it's the result of a virus. In fact, many of these
e-mails are hoaxes. Many online computer virus resources will list
widely circulated hoax e-mails.
You won't get a virus just from reading text
e-mails. Viruses are spread as executable file attachments (files
ending in ". EXE", ". VBS" or ". COM"
for example) or messages containing embedded executable code (such
from opening image files, audio files, text files or pure data files.
However, some viruses can be made to look like an innocent picture
- the file name was anna.jpg.vbs. The .jpg component of the filename
made many computer users think that the file was a picture and distracted
them from the .vbs ending which identifies the file as an executable
Sharing an infected disk spreads many viruses.
These viruses will usually reside in your computer's memory and infect
any floppy disk you place in your drive. Both file viruses and system
sector viruses can be spread by floppy disk. Your best line of defense
is common sense. If you are in doubt about the source of the file
or attachment, don't open it. When a software application is infected,
the virus will attempt to infect any documents accessed by that program.
If the infected computer is on a network, the infection can rapidly
spread to other networked computers that share files. If a copy of
the infected file is transferred to another computer through e-mail
or floppy disk, the virus can spread to that computer. The virus will
continue until it's found and eradicated. Obviously, a virus can't
do any harm if it is caught before it gets a chance to start. You
can use anti-virus (or virus protection) software to check (or "scan")
the files on your hard drive to detect if any of them contain known
viruses. If an infected file is found, most anti-virus programs give
you the option of deleting the infected file or attempting to remove
the virus and leave the uninfected version of the file on your computer.