COMPUTER VIRUS

 A great number of computer problems can be caused by computer
viruses. Effects of a virus could be minor or severe (fatal), and they
might be predictable or sporadic. Unfortunately, diagnosing and
removing viruses can be difficult, and with the increased information
exchange brought on by access to the Internet, viruses are becoming
more and more prevalent.
Computer viruses are not caused by corrupted files or internal OS or
application flaws. Rather, they are intentionally created programs, the
purpose of which is to cause some effect in the computer and replicate
themselves to be passed on to other computers. The effect that a virus
has on a computer is called payload. A virus payload could be
nondestructive to the computer, meaning that it could merely display a
particular message, run a video clip, or change the display colors.
However, if a payload is destructive, it can delete files, close running
applications, or destroy a drive’s master boot record.

                                                           Virus Types

Many types of computer infestations are actually not viruses at all. A true
virus is a piece of code that attaches itself to an executable file and is not
activated until the executable file is launched.
1. Worm is a
program in itself and does not need to attach itself to a legitimate application
in order to run. Viruses are typically more common than worms.
Viruses can be categorized by where they hide themselves.

2. File viruses hide themselves in executable
files. When the executable file is run, the virus is activated.

3. Macro virus attach themselves to
portions of applications and disguise themselves as macros. A macro is
simply an automated process within an application, such as reading and
automatically updating a date field or searching for and formatting specified
text.

4. Boot sector virus hides itself
in the MBR and is activated during startup when the MBR is located and
initialized.
                              Sources and Spreading of Viruses

When a virus is introduced into a computer system, it typically replicates
(copies) itself into memory. From there, it can copy itself into other files in
the system. This is an intentional behavior, configured by the programmer
who created the virus. These copies of the virus can then be spread via floppy
disks, downloading files from the Internet, or executing e-mail attachments
that launch a host program, such as a word processor.
You can minimize the spread of viruses by using antivirus programs that
scan all new files introduced into the computer system. You should scan all
files on floppies that have been used in other computers, all e-mail messages
with attachments, and all files that you download from the Internet.
Detecting and Removing Viruses
Unfortunately, even if you take all the precautions we’ve mentioned, you
are not immune to computer viruses. New viruses are created all the time and
could be too new for your antivirus utility to detect. When the computer starts
behaving sporadically or begins to unexpectedly crash, close, or launch
applications or lose files, you should suspect a virus and begin
troubleshooting the problem immediately. If you have an antivirus utility, run
it and instruct it to perform a virus scan and removal. A variety of antivirus
utilities are available from third parties, such as Norton, Symantec, and
McAffee. Windows 2000 includes a native antivirus utility called AVBoot.
In most cases, antivirus utilities work by recognizing and removing
specific viruses. They are typically useless against viruses that have been
created since the release of the utility itself. For this reason, most third-party
virus utility manufacturers keep an up-to-date list of new viruses and offer
upgrades via the Internet. It is therefore important that you update you
antivirus utility’s capabilities often. Furthermore, if you stay current about
new virus types, you are likely to recognize them more quickly if they are
introduced into your system.
If an antivirus utility has failed to detect and remove a virus and you
suspect the virus is limited to the boot sector, use the FDISK/MBR command.
This command will replace the infected MBR with a (hopefully) good copy
from a floppy disk.
If you are unable to remove a virus before it has caused fatal damage, you
will probably have to reinstall the OS from scratch. It is important in these
cases to repartition and reformat the hard drive because viruses could still
exist on the drive (especially in the boot sector).
Use the following Scenario & Solution questions and answers to test your
knowledge of the virus concepts discussed in the previous
Read Also HOW TO DETECT VIRUS FROM YOUR COMPUTER