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what are computer virus?what are the most dangerous viruses(atleast five and some explanation about them)?which is the best anti virus in world(any five)? |
The
computer system gets infected with a virus through external sources like CD's,
Floppy Disk, USB storage devices and Internet. The virus starts spreading when
start up the program or application that is infected with a virus. For example,
a word processing program containing a virus, places the virus in the computer
memory every time it is run. Once entering the computer memory, the virus may
attach itself to other applications, disks or folders. It may also infect a
network if it has internet connectivity. The Boot Sector Virus
affects the boot sector of a floppy or hard disk. It infects the start-up
instructions which are required to boot the system. The best way of avoiding
boot viruses is to ensure that floppy disks are write-protected and never start
the computer with an unknown floppy disk in the disk drive. The examples of
boot viruses are Danish Boot, Disk Killer etc.
The File viruses
attach to executable files such as .com, .exe, and .dll files by inserting
virus program instructions into the execution sequence. When the infected files
runs, the inserted instructions execute the virus code. After the code finishes
executing, the file continues with its normal execution sequence. This happens
so quickly so the user will not be aware that the virus has become
active. The damage caused by file viruses is very irritating - it displays
screen messages, and also destroys data.
The Macro Virus does
not infect program files. They infect documents. Common targets for many macro
viruses are word processors such as Microsoft Word, and spreadsheets such as
Microsoft Excel. It inserts unwanted text into documents and reduces the
functionality of the computer. Macro viruses that infect Word commonly target
the macros that are associated with the Normal .dot template. This template is
common to all the word files, so all the word files can be infected. Trojan
Horses is a computer virus which is designed to appear innocent but
has been intentionally designed to cause some malicious activities in system.
It can damage files, break password etc. They enter the computer through a
network like Internet while downloading or surfing various websites. One of the
famous Trojan Horse is Black Orifice.
Worm is one of the common computer
threats. It is a program that when run, has the ability to spread to other
computers on the network using the e-mail addresses found on the computer or by
using the Internet, they infect a remote computer. They can use e-mail
address and can send message to everyone without your knowledge.
Resident Virus is a
permanent virus that resides in the RAM memory. It interrupts all of the
operations executed by the system. It corrupts files and programs that are
opened, closed, copied or renamed. The examples of resident virus are Randex,
CMJ, Meve and Mrklunky.
Overwrite Virus is
designed to delete the information contained in the files. The only way to
clean a file infected by an overwrite virus is to delete the file completely,
thus losing the original content. The examples of this virus include Way, Trj.
Reboot, Trivial.88.D.
Dangerous Viruses: 1 )
Jerusalem – 1987 This is
one of the first MS-DOS viruses in history that caused enormous destructions,
affecting many countries, universities and company worldwide. On
Friday 13, 1988 the computer virus managed to infect a number of institutions
in Europe, America and the Middle East. The name was given to the virus after
one of the first places that got “acquainted” with it – the Jerusalem
University. 2 )
Morris (a.k.a. Internet Worm) – November 1988 The Morris worm or Internet
worm was one of the first computer worms distributed via the Internet. It is
considered the first worm and was certainly the first to gain significant
mainstream media attention. It also resulted in the first conviction in the US under the
1986 Computer Fraud and Abuse Act. Once the worm discovers an internet
connection, all that it must do is download a copy of itself to that location,
and continue running as normal. Now it has been 7 years since the Worm
was defeated, but it is still worth looking at what happened, both in terms of
how the program operated, and as to what conditions allowed it to do what it
did. With that in mind, there are a number of subtopics of interest. 3 )
Solar Sunrise – 1998: Two
Californian teenagers took American government by surprise, in 1998, when they
intruded and took control of around 500 systems that belonged to the
governmental as well as private sector. This was done with the help of a
computer virus and the situation was given the name of Solar Sunrise, after an
operating system called Sun Solaris. The computers that ran this OS had few
weaknesses. US government took the incident as another golden opportunity to
blame Iraqis but soon found out that the culprits were no other than their own
Americans. 4 )
Melissa – 1999 The Melissa virus, also known
as “Mailissa”, “Simpsons”, “Kwyjibo”, or “Kwejeebo”, is a mass-mailing macro
virus. As it is not a standalone program, it is not in fact a worm. Melissa can
spread on word processors Microsoft Word 97 and Word 2000 and also Microsoft
Excel 97, 2000 and 2003. It can mass-mail itself from e-mail client Microsoft
Outlook 97 or Outlook 98. If a Word document containing the virus,
either LIST.DOC or another infected file, is downloaded and opened, then the
macro in the document runs and attempts to mass mail itself. When the
macro mass-mails, it collects the first 50 entries from the alias list or
address book and sends itself to the e-mail addresses in
those entries.
5 ) I
Love You – May 2000 This is one of the most
dangerous worms ever and spread worldwide in only one night. It infected around
ten percent of all internet users, and the monetary loss was around $5.5
billion. The process started when a user received an email with the subject
“ILOVEYOU†and an attachment “LOVE-LETTER-FOR-YOU.TXT.vbsâ€. As soon as
the file was opened, the virus managed to send its copy to every address
present in the Windows Address Book. This worm was written by a Filipino student who was punished as Philippines had no law
related to such cyber crimes. Perhaps this incident triggered the creation of
European Union’s global Cybercrime Treaty.
6 ) The
Code Red worm – July 2001 The Code Red worm was a computer worm observed on
the Internet on July 13, 2001. It attacked computers running Microsoft’s
IIS web server. The Code Red worm was first discovered and researched by
eEye DigitalSecurity employees Marc
Maiffret and Ryan Permeh. The worm was named the .ida “Code Red” worm because
Code Red Mountain Dew was what they were drinking at the time, and because of
the phrase “Hacked by Chinese!” with which the worm defaced websites.
7 )
Nimda – 2001 Nimda
is a computer worm, and is also a file infector. It quickly spread, eclipsing
the economic damage caused by past outbreaks such as Code Red. Multiple
propagation vectors allowed Nimda to become the Internet’s most widespread
virus/worm within 22 minutes. The worm was released on September 18,
2001. Nimda was considered to be one of the most complicated viruses, having up
to 5 different methods of infecting computers systems and duplicating itself. 8 )
Downadup – 2009 The
Downadup worm, also known as Conficker and Kido, has affected 6 million PCs in
just the past three days, according to British officials. his malicious program
was able to spread using a patched Windows flaw. Downadup was successful in
spreading across the Web due to the fact that it used a flaw that Microsoft
patched in October in order to distantly compromise computers that ran
unpatched versions of Microsoft’s operating system. According to New York
Times, conficker has more than 7 million computer systems under its control
now. China, Argentina, Brazil, Russia, and India were the main affected
nations.
Anti Viruses Anti-virus
software is an application program that detects and removes viruses from
the system. When executed, this anti-virus software program looks for viruses
in all the files, folders and drives of the computer. If virus is detected then
it lists all the viruses present in the computer. It also cures or deletes
listed viruses from the system. The most commonly used anti-virus software are
Symantec Antivirus and McAfee Antivirus Software. Symantec
Antivirus is one of the most commonly used anti-virus programs. It has been
developed by Symantec Corporation. It helps to scan files, folders, drives etc.
for viruses. While scanning, if any of the viruses is found it removes it from
the system or prevents its action. The Norton Anti-virus removes Trojan horse,
worms, viruses etc. from computer system. It also checks your e-mails, its
attachments and documents for viruses. Most popular Anti Viruses are: 1) Microsoft Security Essentials : This antivirus is from
Microsoft team and totally free for Genuine Windows users. It has a good
detection rates and most of all very light on resources. Automatic updates
works perfectly fine. To see the whole review and how to install MSE on your
computer, please click this link. 2) Avast ! Free Antivirus : Avast is often seen as the biggest
competitor to other Antivirus programs as it is very simple and easy to use.
Avast is loaded with most features, real-time protection capabilities including
web, E-mail, P2P, network shields, boot-time scanning. It is very light
onresources and hardly take minutes to schedule scans. But there is one
negative point that you have to register first and it takes time to register.
Otherwise it is widely preferredAntivirus program for many users. 3) AVG Free Antivirus : AVG has been around in the Antivirus
market from ages and gained lot of loyal users to their kitty. They also
provide upgraded version which is very costly but I believe that their
freeAntivirus program is great for users having personal computers. AVG user
interface is pretty simple and it takes a minute to install on your computer. 4) Bitdefender : Bitdefender is one of the best contender for top
Antivirus software which provides advanced protection against viruses, phishing
attacks, spyware, malwaere and various other real-time threats. It takes only
minutes to download it and work without slowing downyour computer speed. There
is also a very nifty feature included in the latest version that it helps to
protect leaking your personal information via E-mail, Web or IM. 5) Avira AntiVir Personal : One of the best pick if you are
looking for simple to use and light on Antivirus software. It works perfectly
fine to detect virus, spyware, rootkit threats. The best part of Avira is that
it is quiet outstanding in terms of finding malware. Few false positives about
Avira is that it does not inlude E-mail scanner in free version, but if you
open any infected E-mail, it comes again into action. And with every update, it
shows advertisements but you have choice to disable them. I still believe that
Avira is strong Antivirus program and you should try it. 6) Como do Antivirus + Firewall: This program was started as a
commerial Antivirus software but now available free for both personal and
commercial use. It is very simple to use, light on resources and doesn’t affect
your computer speed. It offers real-time scanning, automatic updates, email
scanning, detects worms and spyware. The virus definition is update daily and
Host Intrusion Detection allows you to protect from attacking viruses, spyware,
and other malware before they infect your computer. 7) A – Squared Free: This program was detecting and removing only Trojans
in the starting but recently included the Ikarus antivirus engine. It scans
your computer from Trojans, Viruses, Spyware, Adware, Worms, Bots, Key loggers
and Dialers. The only negative point about this software is its large virus
update size. Its comes with Antivirus + Anti – Spyware. 8 ) Rising Antivirus : Rising Antivirus Free Edition is Antivirus
solution from China. It is a simple program which runs low on the memory and do
every bit of task that every other Antivirus software does. It protects
computers against all types of viruses, Trojans, worms, root kits and other
malicious programs. One feature is good is that it provides full protection to
your account information. It mostly updates on alternate days and if you are
looking for “install and forget” program, this program is best. 9) PC Tools Antivirus: All-in-one program which can protect your
PC from virus, worms, Trojans and also included scanning of incoming and
outgoing mails. It provides you on-demand scans and automatic updates. The
negative points are that free edition offers limited support and updates are
non-priority based which are essential for real-time virus protection program. 10) Spyware Doctor with Antivirus 2010 : As the name suggests, its
comes with Anti-spyware and Antivirus program which provides full security to
your computer. It detects almost every infection like spyware, adware, Trojans,
viruses, worms, key loggers, identity theft, phishing, popups and malicious
websites. It updates automatically mostly on daily basis. Top 5 Free Antivirus Software AOL Active Virus Shield |
