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.
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.
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