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The most common blunder people make when the topic of a computer virus arises is to refer
to a worm or
Trojan horse as
a virus. While the
words Trojan, worm and virus are often used interchangeably, they are not
exactly
the same. Viruses, worms and Trojan Horses are all malicious
programs that can
cause damage to your
computer, but there are differences among the three, and knowing those
differences can help you to better protect your computer from their often
damaging effects.
What Is a Virus?A computer virus
attaches itself to a program or
file enabling it to spread from one computer to
another, leaving infections as it travels. Like a human virus, a computer
virus can range in severity: some may cause only mildly annoying effects
while others can damage your
hardware,
software or
files.
Almost all
viruses are attached to an
executable file,
which means the virus may exist on your computer but it actually cannot infect your
computer unless you run or open the malicious program. It is important to note
that a virus cannot be spread without a human action, (such as running an
infected program) to keep it going.
People continue the spread of a computer
virus, mostly unknowingly, by sharing infecting files or sending
e-mails with viruses
as attachments in the e-mail.
What Is a Worm?A worm is
similar to a virus by design and is considered to be a sub-class of a
virus. Worms spread from computer to computer, but unlike a virus, it has the
capability to travel without any human action. A worm takes advantage of file
or information transport features on your system, which is what allows it to travel unaided.
The biggest danger with a worm is its capability to replicate itself on your system, so rather than your computer sending out a single worm, it could send out
hundreds or thousands of copies of itself, creating a huge devastating effect. One
example would be for a worm to send a copy of itself to everyone listed in your
e-mail address book. Then, the worm replicates and sends itself out to everyone
listed in each of the receiver's address book, and the manifest continues on
down the line. Due to the copying nature of a worm
and its capability to travel across networks the end result in most cases is that
the worm consumes too much
system memory (or
network bandwidth), causing Web
servers, network
servers and individual computers to stop responding. In recent worm
attacks such as the much-talked-about Blaster Worm, the worm has been designed
to tunnel into your system and allow malicious users to control your computer
remotely.
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Key Terms To
Understanding Computer Viruses
virus
A program or piece of code that is loaded onto your computer without
your knowledge and runs against your wishes.
Trojan Horse
A destructive program that masquerades as a benign application.
Unlike viruses, Trojan horses do not replicate themselves
worm
A program or algorithm that replicates itself over a computer
network and usually performs malicious actions
blended threat
Blended threats combine the characteristics of viruses, worms,
Trojan Horses, and malicious code with server and Internet
vulnerabilities .
antivirus program
A utility that searches a hard disk for viruses and removes any that
are found.
Related Webopedia
Articles
The Differences and Features of Hardware & Software Firewalls
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Antivirus and Antispyware Software: What's The Difference?
Rogue Anti-Virus Software Explained |
What Is a Trojan horse? A Trojan
Horse is full of as much trickery as the mythological Trojan Horse it
was named after. The Trojan Horse, at first glance will appear to be useful
software but will actually do damage once installed or run on your computer. Those on the receiving end of a Trojan
Horse are usually tricked into opening them because they appear to be receiving legitimate
software or files from a legitimate source. When a Trojan is activated on
your computer, the results can vary. Some Trojans are designed to be more
annoying than malicious (like changing your
desktop, adding silly active desktop
icons) or they can cause serious damage by deleting files and destroying
information on your system. Trojans are also known to create a
backdoor on your
computer that gives malicious users access to your system, possibly allowing
confidential or personal information to be compromised.
Unlike viruses and worms, Trojans do not reproduce by infecting other files nor
do they self-replicate.
What Are Blended Threats?Added into the mix, we also have what is
called a blended threat. A blended threat is a
more sophisticated attack that bundles some of the worst aspects of viruses,
worms, Trojan horses and malicious code into one single threat. Blended threats
can use server and Internet vulnerabilities to initiate, then transmit and
also spread an attack. Characteristics of blended threats are that they cause harm
to the infected system or network, they propagates using multiple methods,
the attack can come from
multiple points, and blended threats also exploit vulnerabilities.
To be considered a blended thread, the attack
would normally serve to transport multiple attacks in one payload. For
example it wouldn't just launch a DoS attack it would also, for
example, install a
backdoor and maybe even damage a local system in one shot. Additionally, blended threats
are designed to use multiple modes of transport. So, while a worm may
travel and spread through e-mail, a single blended threat could use multiple routes
including e-mail, IRC and file-sharing sharing networks.
Lastly, rather than a
specific attack on predetermined .exe files, a blended thread could do
multiple malicious acts, like modify your
exe files, HTML files and registry keys at the same time basically it can
cause damage within several areas of your network at one time.
Blended threats are considered to be the
worst risk to security since the inception of viruses, as most blended threats
also require no human intervention to propagate.
Combating Viruses, Worms and Trojan
Horses The first step in
protecting your computer from any malicious there is to ensure that your
operating system
(OS) is up-to-date. This is essential if you are running a Microsoft Windows OS.
Secondly, you need to have
anti-virus software installed on your system and ensure you
download updates
frequently to ensure your software has the latest fixes for new viruses, worms,
and Trojan horses. Additionally, you want to make sure your anti-virus program
has the capability to scan e-mail and files as they are downloaded from the
Internet, and you also need to run full disk scans periodically. This will help prevent malicious programs from even reaching your
computer. You should also install a
firewall as well.
A firewall is a system that prevents unauthorized
use and access to your computer. A firewall can be either hardware or software.
Hardware firewalls provide a strong degree of protection from most forms of
attack coming from the outside world and can be purchased as a
stand-alone product or in broadband
routers. Unfortunately, when battling viruses,
worms and Trojans, a hardware firewall may be less effective than a software
firewall, as it could possibly ignore embedded worms in out going e-mails and
see this as regular network traffic.
For individual home users, the most popular firewall
choice is a software firewall. A good
software firewall will protect your computer from outside attempts to control or gain
access your computer, and usually provides additional protection against the most common Trojan programs or e-mail
worms. The downside to software firewalls is that they will only
protect the computer they are installed on, not a network.
It is important to remember that on its own a
firewall is not going to rid you of your computer virus problems, but
when used in conjunction with regular operating system updates and a good anti-virus
scanning software, it will add some extra security and protection for your computer
or network.
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Did You Know...
CodeRed, a blended threat, launched DoS attacks, defaced Web
servers, and its variant, CodeRed II, left Trojan horses behind
for later execution. CodeRed was processed in memory not on a
hard disk allowing it to slip past some anti-virus products.
Computer Economics has estimated the worldwide cost of CodeRed
at $2.62 billion dollars.
[Source:
Symantec Web
site] |
Want more PC security
Guides?
Be sure to
read the article,
"Did You Know...
The Differences and Features of
Hardware & Software Firewalls".
Based in Nova Scotia, Vangie Beal is has been
writing about technology for more than a decade. She is a frequent
contributor to
EcommerceGuide and
managing editor at
Webopedia. You can
tweet her online @AuroraGG
Last updated: September 25, 2009 Originally
Published 2004
Webopedia's The Differences and Features of Hardware & Software Firewalls

Firewalls can be either hardware or software. The ideal firewall configuration
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Webopedia's Did You Know... All About Phishing

An e-mail scam is a fraudulent e-mail that appears to be from a legitimate
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information or account details.
Webopedia's Did You Know... Understanding Rootkits

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As technology advances and more people come to rely on the Internet for
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Webopedia's Antivirus and Antispyware Software: What's The Difference?

In this Did You Know article, we discuss two areas
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Webopedia's Did You Know... How to Deal With Pop-ups 
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Microsoft's Protect
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At home or at work, Microsoft's Protect Your PC Web site offers an excellent
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