-: What is a computer worm?
Well, a worm is a piece of malicious software,
much like a virus.
But it has a key difference.
A worm can replicate itself without any user interaction.
If you remember when I talked about viruses,
I said that a user has to install a program,
or open a file, for that virus to be able
to take its action.
But with worms, that's simply not the case.
Worms are able to self-replicate and spread
throughout your network, without a user's consent,
or their action.
This occurs because worms take advantage
of security holes in operating systems and applications.
So, if a worm knows that there's somebody out there
who hasn't installed a security patch,
they can take advantage of that, and use that to spread
from victim to victim, across the network,
and across the world.
Because of this, worms can cause disruption
to your normal network traffic, and computing activities.
This is because they're spreading and replicating
really fast.
And when they do this from your victim machine,
They're using up computing power.
Its processing power, its memory,
and its network traffic capability.
And all of that is going to start slowing down your system.
In some cases, this can even cause your system to crash.
Worms are known for spreading far and wide
over the Internet, in a very short amount of time.
Back in 2001, there was a worm named Nimda,
which is admin spelled backwards.
It was able to propagate across the entire Internet
in just 22 minutes.
Then, in 2009, there was another worm, called Conficker.
This is probably one of the largest worms
that we've seen to date.
It was able to infect between nine and 15 million machines.
This worm was going through and infecting as many machines
as it could, and any machines it found that was missing
a Microsoft operating system patch,
specifically the Microsoft 08-067 patch, they would infect.
This patch was solving a software bug
inside the way Windows was doing file and printer sharing.
Conficker sought out these victim machines,
installed a piece of code, and they all became part
of its botnet.
Ultimately, this botnet was able to be shut down
before it was used for a negative or a nefarious purpose,
but it does show the true power of these worms,
and how far and wide they can spread across the Internet.