The worm is a piece of virus that creates a copy of itself while using a computer network.
In 1988, the first worm was introduced. Its name was Internet worm.
A worm spread through an email attachment. When you open an email attachment containing a worm in your system, this will not only affect your system. But if you send it to another, it will affect that system too.
Worm jump to the systems that have vulnerability. Then these computers/systems are used for worm propagation to other computers. This process in which the worm moves the affective system to other is known as direct propagation.
Example of Slammer worm
The Slammer worm detonated through the Internet on January 25, 2003. Slammer had infected 90% of all vulnerable computers on the entire Internet within 10 minutes before people knew about it.
Damage Slammer worm create
Although Slammer did not remove the hard disk, it caused massive damage by spreading so quickly. Around the world, ATMs became useless. Even police departments lost their ability to communicate, and most users in Korea lost their service.
These facts were confirmed by Raymond R. Panko, in 2003.
So as faster and more, it is sent to systems, it will affect as many.
There are two most successful and impactful worms
It was noticed, in 2001, by exploiting a vulnerability in a server called Microsoft internet information server, the worm can damage hundreds of thousands of systems.
It is also the most harmful worm introduced in 2003. It creates vulnerability in Microsoft RPC services, and by doing this, it can affect hundreds of thousands of system