10 Worst Computer Viruses of All Time

10 Worst Computer Viruses of All Time

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Computer viruses can be a nightmare. Some can wipe out the information on a hard drive, tie up traffic on a computer network for hours, turn an innocent machine into a zombie and replicate and send themselves to other computers. If you've never had a machine fall victim to a computer virus, you may wonder what the fuss is about. A Fox News report estimated that around $86 billion is lost worldwide annually due to malwares, email viruses and worms.

While some pranksters created virus-like programs for large computer systems, it was really the introduction of the personal computer that brought computer viruses to the public's attention. A doctoral student named Fred Cohen was the first to describe self-replicating programs designed to modify computers as "viruses". The name has stuck ever since. 

Today we're going to take a look at 10 of the worst computer viruses to cripple a computer system. Let's start with no. 10, the Melissa virus.

10. Melissa

In the spring of 1999, a man named David L. Smith created a computer virus based on a Microsoft Word macro. He built the virus so that it could spread through e-mail messages. Smith named the virus "Melissa," saying that he named it after an exotic dancer from Florida. (Source : CNN)

Smith during his Court Trials

Rather than shaking its moneymaker, the Melissa computer virus tempts recipients into opening a document with an e-mail message like "Here is that document you asked for, don't show it to anybody else." Once activated, the virus replicates itself and sends itself out to the top 50 people in the recipient's e-mail address book.

9. I love You

A year after the Melissa virus hit the Internet, a digital menace emerged from the Philippines. Unlike the Melissa virus, this threat came in the form of a worm -- it was a standalone programcapable of replicating itself. It bore the name ILOVEYOU. 

According to anti-virus software producer McAfee, the ILOVEYOU virus had a wide range of attacks:

• It copied itself several times and hid the copies in several folders on the victim's hard drive.
• It added new files to the victim's registry keys.
• It replaced several different kinds of files with copies of itself.
• It sent itself through Internet Relay Chat clients as well as e-mail.
• It downloaded a file called WIN-BUGSFIX.EXE from the Internet and executed it. Rather than fix bugs, this program was a password-stealing application that e-mailed secret information to the hacker's e-mail address.

Who created ILOVEYOU virus was never found, but as per estimates ILOVEYOU virus caused $10 billion in damages.

8. The Klez Virus

The Klez virus marked a new direction for computer viruses, setting the bar high for those that would follow. It debuted in late 2001, and variations of the virus plagued the Internet for several months. The basic Klez worm infected a victim's computer through an e-mail message, replicated itself and then sent itself to people in the victim's address book. 

Some variations of the Klez virus carried other harmful programs that could render a victim's computer inoperable.
Shortly after it appeared on the Internet, hackers modified the Klez virus in a way that made it far more effective. Like other viruses, it could comb through a victim's address book and send itself to contacts. Also they made the virus intelligent enough to spoof the email address from where it was coming.

7. Code Red and Code Red II

The Code Red and Code Red II worms popped up in the summer of 2001. Both worms exploited an Operating system vulnerability that was found in machines running Windows 2000 and Windows NT. The vulnerability was a buffer overflow problem, which means when a machine running on these operating systems receives more information than its buffers can handle, it starts to overwrite adjacent memory.

The original Code Red worm initiated a distributed denial of service (DDoS) attack on the White House. That means all the computers infected with Code Red tried to contact the Web Servers at the White House at the same time, overloading the machines. 
A Windows 2000 machine infected by the Code Red II worm no longer obeys the owner. That's because the worm creates a backdoor into the computer's operating system, allowing a remote user to access and control the machine.

6. Nimda

Another virus to hit the Internet in 2001 was the Nimda (which is admin spelled backwards) worm. Nimda spread through the Internet rapidly, becoming the fastest propagating computer virus at that time. In fact, according to TruSecure CTO Peter Tippett, it only took 22 minutes from the moment Nimda hit the Internet to reach the top of the list of reported attacks.

The Nimda worm's primary targets were Internet servers. While it could infect a home PC, its real purpose was to bring Internet traffic to a crawl. It could travel through the Internet using multiple methods, including e-mail. This helped spread the virus across multiple servers in record time. 

5. SQL Spammer / Sapphire 

In late January 2003, a new Web Server virus spread across the Internet. Many computer networks were unprepared for the attack, and as a result the virus brought down several important systems. The Bank of America's ATM service crashed, the city of Seattle suffered outages in 911 service and Continental Airlines had to cancel several flights due to electronic ticketing and check-in errors.

The culprit was the SQL Slammer virus, also known as Sapphire. By some estimates, the virus caused more than $1 billion in damages before patches and antivirus software caught up to the problem.

4. MyDoom

The MyDoom (or Novarg) virus is another worm that can create a backdoor in the victim computer's operating system. The original MyDoom virus -- there have been several variants -- had two triggers. One trigger caused the virus to begin a denial of service (DoS) attack starting Feb. 1, 2004. 

The second trigger commanded the virus to stop distributing itself on Feb. 12, 2004. Even after the virus stopped spreading, the backdoors created during the initial infections remained active.

3. Sasser and Netsky

The Sasser worm attacked computers through a Microsoft Windows vulnerability. Unlike other worms, it didn't spread through e-mail. Instead, once the virus infected a computer, it looked for other vulnerable systems. It contacted those systems and instructed them to download the virus. The virus would scan random IP addresses to find potential victims. The virus also altered the victim's operating system in a way that made it difficult to shut down the computer without cutting off power to the system. 

At one time, security experts at Sophos believed Netsky and its variants accounted for 25 percentof all computer viruses on the Internet.
A 17-year-old German named Sven Jaschan created the two programs and unleashed them onto the Internet.

2. Leap-A / Oompa-A

In 2006, the Leap-A virus, also known as Oompa-A, debuted. It uses the iChat instant messaging program to propagate across vulnerable Mac computers. After the virus infects a Mac, it searches through the iChat contacts and sends a message to each person on the list. The message contains a corrupted file that appears to be an innocent JPEG image. 

The Leap-A virus doesn't cause much harm to computers, but it does show that even a Mac computer can fall prey to malicious software. 

1. Storm Worm

The latest virus on our list is the dreaded Storm Worm. It was late 2006 when computer securityexperts first identified the worm. The public began to call the virus the Storm Worm because one of the e-mail messages carrying the virus had as its subject "230 dead as storm batters Europe." Antivirus companies call the worm other names. 

The Storm Worm is a Trojan horse program. Its payload is another program, though not always the same one. Some versions of the Storm Worm turn computers into zombies or bots. As computers become infected, they become vulnerable to remote control by the person behind the attack 

NEED TEAM MEMBERS TO BUILD A VIRUS LIKE THIS....FUTURE VIRUS ....