Nov 18, 2012

COMPUTER VIRUSES

                                 COMPUTER VIRUSES   
   
WHAT IS THE COMPUTER VIRUS: A computer virus is a program or piece of code that operates by attaching itself to some other program or downloaded file.When this program starts, the virus code unintentionally runs,replicates itself and infects other programs or documents on the PC.A computer virus spreads mainly via e-mail attachments,downloadable files from the internet or floppy discs.Virus infection can be prevented  by installing anti-virus software,among other strategies, some of which are outlined in this advice sheet.

A computer virus can seriously damage or completely destroy files or software on a computer.The result is that files may be lost permanently,educational programs may not function correctly or the overall performance of a computer may be slowed down. The process involved in repairing the damage can be time consuming and expensive.

COMMON VIRUS INFECTION SYMPTOMS: Viruses can effect your computer in many ways.Although there are no telltale signs of a virus,there are a few symptoms that may suggest that your computer has a virus -----

1> Unexplained messages appear on the screen.
2> Specific files are mysteriously deleted.
3> Unknown files are added to a disc.
4> An entire disc or drive is erased.
5> The keyboard does not work properly.
6> Unexplained modifications are made to data or documents.
7> Application software seems to be changed.
8> Operating system software appears to be modified.
9> Unexplained printing problems occur.

TYPES OF VIRUSES:  Some of the most common types of computer viruses are .......


A>TROJAN HORSE: A Trojan horse program has the appearance of having a useful and desired function.While it may advertise its activity after launching,this information is not apparent to the user beforehand.Secretly the program performs other, undesired functions.A Trojan horse neither replicates nor copies itself,but causes damage or compromises the security of the computer.A Trojan horse must be sent by someone or carried by another program and may arrive in the form of a joke program or software of some sort.The malicious functionality of a Trojan horse may be anything undesirable for a computer user,including data destruction or compromising a system by providing a means for another computer to gain access,thus bypassing normal access controls.


B>WORMS: A Worm is a program that makes and facilitates the distribution of copies of itself, for example,from one disk drive to another or by copying itself using e-mail or another transport mechanism.The worm may do damage and compromise the security of the computer.It may arrive via exploitation of a system vulnerability or by clicking on an infected e-mail.


C>BOOT SECTOR VIRUS: A virus which attaches itself to the first part of the hard disk that is read by the computer upon bootup.These are normally spread by floppy disks.


D>MACRO VIRUS: Macro viruses are viruses that use another applications macro programming language to distribute themselves.They infect documents such as ms word or ms excel and are typically spread to other similar documents.


E>MEMORY RESIDENT VIRUS: Memory resident viruses reside in a computers volatile memory(RAM).They are initiated from a virus which runs on the computer and they stay in memory after its initiating program closes.


F>ROOTKIT VIRUS: A Rootkit virus is an undetectable virus which attempts to allow someone to gain control of a computer system.The term Rootkit comes from the Linux administrator root user.These viruses are usually installed by Trojans and are normally disguised as operating system files.


G>POLYMORPHIC VIRUS: A Polymorphic virus not only replicates itself by creating multiple files of itself,but it also changes its digital signature every time it replicates.This makes it difficult for less sophisticated antivirus software to detect.


H>LOGIC BOMBS/TIME BOMBS: These are viruses which are programmed to initiate at a specific date or when a specific event occurs.Some examples are a virus which deletes your photos on Halloween ,or a virus which deletes a database table if a certain employee gets fired.



WHAT KIND OF DAMAGE CAN COMPUTER VIRUSES DO: 

1>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.

2>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.


3>Some viruses can slow down your system dramatically.


4>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.


5>Other viruses , like the internet worm that hit recently,also can have widespread effects on computer networks and the internet.



PREVENTING VIRUS INFECTION:


a>Install and regularly update anti-virus. This in conjunction with good housekeeping,can greatly reduce the threat caused by computer viruses.


b>All floppy disks or other removal media,should remain within the confines of the computer room.It is not advisable to let students bring them home or return with them to school.However,if this occurs they should be scanned immediately using anti-virus software.Floppies should also be write protected.


c>Files should be saved to a designated hard drive where incoming files can be scanned automatically by anti-virus software.


d>When the sender of an e-mail is not known to the recipient,avoid clicking on attachments containing an executable file.


e>Creating back-ups of files won't directly prevent virus infection, but it may speed up the recovery process in the event of a virus erasing or damaging files.


SOME GOOD ANTIVIRUSES:

a> Kaspersky Antivirus.
b> Bit Defender Antivirus.
c> Trend Micro Antivirus.
d> Norton Antivirus.
e> Avast Antivirus.
f> Mcafree Antivirus.
g> Panda Pro Antivirus.
h> Zone Alarm Antivirus.
i> ESET NOD30 Antivirus.
j> AVG Antivirus.
k> F- Secure Antivirus.

                           

                          

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