The most dangerous viruses of the century are listed below:
Jerusalem
This is a DOS(Disc Operating System) based computer virus which was detected during 1988. Jerusalem University is the first place that the virus attacked. This is the reason for the name of the virus. It affected many parts of the world including US etc.
Internet Worm
Internet worm is termed with the code name Morris. It was first detected in November 1988. This virus does nothing but transmit files from one computer to another and their by eats the entire bandwidth. So the computers connected to the network stops responding.
This virus affected more than 5000 computers including NASA computer center. This virus is so intelligent that it can pickup the passwords of the users if requires. This is one of the major security threat during the 20th century.
Melissa
This is one of the most toughest viruses detected. This virus sends the emails to all the users in the address book of the affected computer. The virus loads with the file namely "List.DiC" which is loaded with the passwords of the pornographic sites.
This virus starts affected on March 26, 1999. It was developed by a New Jersey based computer engineer, David L. Smith.
The virus will mail to all the contacts stored in the Microsoft Outlook 97/98 address book. It can also send the passwords of the users back to the creator of the virus.
I Love You
This virus is much similar to the Melisa virus in its functionalities. It was created in May 2000 by a Philippines based student. Though he caught by the Police, they could not sentence him to the prison as there were no law supporting the cyber crime in the country. It made the people to create a common organization which define the law for cyber crime cases called European Union's Global Cyber Crime Treaty.
This virus will affect from a mail with the subject "I Love You" which gave the name to the virus. It affected millions of computers in a single day which tells us the importance of the word "Love" :)
The Code Red Worm
This is one of the strange virus developed by some of the unhappy people of US system. It is developed to attack "White House" website on a predetermined date. It uses many computers across the world to flood with the requests and their by crash the website.
This virus was detected in July 2001.
Downadup
The latest and most dangerous virus started affecting in this year. It uses a flaw in the Microsoft Windows OS. Microsoft had given a patch to a flaw in October 2008. This virus uses this flaw and affects all computers that do not have the patch installed.
It is detected that about 3 million computers have affected with this virus. The other name for this virus is Conficker.
