The 10 Most Dangerous Computer Viruses Ever

As we go about our day-to-day lives completely plugged in to the Internet via our laptops and smartphones, we become walking focal points of data just waiting to be captured and exploited. It almost makes you long for the early days of popular computing, when Windows 95/98 was king and email was an exciting new technology. At least then you didn’t have to worry about compromising your credit card information – because you didn’t shop online, since that wasn’t really a thing. As more and more of our business functions take place in the online world, we become more and more vulnerable to attacks by malicious individuals looking to steal that valuable information. The large majority of us are blissfully unaware how the processors in our phones even work or what language the operating system is built in, let alone how to properly configure and defend against an attack from someone who actually does know what they’re doing.

The pandemonium around computer viruses has ebbed and flowed at different times, usually upon the introduction of new Internet technology. Because 99% of people don’t understand how their web browsers work, let alone a sophisticated piece of malware, the scares concerning viruses haven’t really helped people avoid them. Strange emails with worms attached will always be opened by clueless folk, and viruses will always find their way into systems. However, not all viruses are created equal. Sometimes they just slow down your computer or smartphone, other times they can log your keystrokes and gain access to all of your passwords and everything you type, and sometimes, they can be far, far more devastating than just that. These viruses fall under the latter category; malicious software programmed to destroy and replicate itself quickly and efficiently across the entire internet, causing millions – sometimes billions – of dollars in damages in the process. These are the 10 most dangerous computer viruses in history.

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10 #10 Conficker

Via wikimedia.org

Conficker was a computer worm that targeted Microsoft operating systems that emerged in 2008. Extremely difficult to detect, Conficker can spread by email, USB drive, external hard drives, or even smartphones. Once infected, the worm links the computer into a botnet – a linked network of ‘zombie’ computers that can be controlled by the creator of the worm – which can be used for denial of service attacks (DoS) or to gather important financial information.

9 #9 Storm Worm

Via zdnet.com

Storm Worm was a virus that functioned much like Conficker, infecting computers and turning them into zombies to participate in a botnet. It began spreading in 2006 through an email with the subject line ‘230 dead as storm batters Europe’. Soon after it altered the nature of its 'bad news', including news updates that stated World War 3 had begun. It quickly spread throughout the Internet, causing as much as 8% of all malware infections worldwide and infecting a little under 10 million PC’s.

8 #8 CIH

Via youtube.com

Occasionally the architects of computer viruses really do have an honorable intention, which is the case for Taiwan’s Chen Ing-hau, who created the CIH (also known as ‘Chernobyl’) virus in 1998. Chen created the virus to demonstrate how vulnerable the computer network at the school he was attending, Tatung University, was to attacks. The virus soon spread rapidly beyond the university, spreading around the world. CIH was a destructive virus that rewrote the BIOS of infected targets, making them completely useless and unable to even boot up. It caused $250 million in damages worldwide, but because there was no legislation for this kind of attack and no one stepped forward with a lawsuit, Chen got away with just a slap on the wrist. One of the world’s most expensive wrist slaps ever.

7 #7 Melissa

Via youtube.com

In 1999, a virus named Melissa spread through email in a similar fashion as CIH. It caused $300 - $600 million in damages and forced the FBI to institute the largest Internet manhunt in history at that time. In the end they found Melissa’s author, David L. Smith, who spent 20 months in federal prison and paid a $5,000 fine – which isn’t really that much all things considered.

6 #6 SQL Slammer

Via docstoc.com

SQL Slammer (also known as ‘Sapphire’) was a worm that spread so rapidly and efficiently that it effectively slowed down the entire speed of the Internet worldwide once it broke loose. It infected 75,000 hosts within 10 minutes of launch in January 2003, mostly in South Korea, but by the end of the day it was worldwide. It caused delays in ATM’s, 911 services, and other essential services. It caused $950 million to $1.2 billion in damages worldwide, all in just one weekend. The program’s tiny size (just 376 bytes) allowed it be sent in one single packet, making it easy to fire from one computer to the next in milliseconds.

5 #5 Code Red

Via businessinsider.com

In 2001, a virus emerged that was designed by unknown Chinese sources. The worm wasn’t spread through email, but rather through web browsers. Infected targets would host websites that would then transmit the virus to visitors, replacing the site with a simple text that simply said ‘Hacked by Chinese!’ It brought down 400,000 servers worldwide, including the White House web server, and caused $2.6 billion in damages.

4 #4 Sobig F

Via uxsup.csx.ac.uk

Sobig F was the 6th variation of the Sobig worm, which spread through emails in August 2003. Once the file in the email was opened, Sobig F would send copies of itself to all contacts in the contact list, and within 24 hours had become the fastest spreading virus in history (at that time), infecting 1 million PC’s and causing $3 - $4 billion in damages.


Via carlosprinte.blogspot.com

The ILOVEYOU virus was spread through emails, and came attached with the particular intriguing subject line ‘ILOVEYOU’. Attached was a file that was named ‘Love-Letter-For-You.TXT.vbs’, which many, many people opened. Back in 2000, awareness of computer viruses was quite low, and many people were enticed by the desire to find out who was secretly in love with them. The virus originated from the Philippines, and caused an estimated $5.5 billion in damages.

2 #2 Mydoom

Via cipherdyne.org

Mydoom is the fastest spreading computer worm in history, and to this day no one knows who created it. A text file in the source code saying ‘andy; I’m just doing my job, nothing personal, sorry’ has led experts to believe that the programmer was paid (handsomely) for his services by groups involved in the email spam business. Within 24 hours of its launch in late January 2004, it had infected millions of computers worldwide by spreading through email. Mydoom created a massive botnet that executed DDoS attacks on internet giants such as Microsoft and Google, shutting the latter down for a large portion of the day. Mydoom caused an unprecedented amount of damage worldwide that has yet to be replicated, with an estimated $38 billion being spent to fight the virus and repair the damage caused.

1 #1 Stuxnet

Via iformbuilder.com

Stuxnet is far and away the #1 entry on this list, and in truth it doesn’t even remotely resemble any other virus that’s been unleashed on the Internet before. Stuxnet wasn’t built to collect credit card information, account passwords, or anything as mundane as that; Stuxnet was a joint American-Israeli cyberweapon designed to destroy Iran’s nuclear power plant and slow down or destroy any progress they’ve made at developing nuclear weapons. The Iranians discovered the Stuxnet worm in their nuclear plant control system in 2010, but they believe it had been present and unnoticed for an entire year prior to discovery. Stuxnet worked by gradually and subtly increasing the rotation speed of the nuclear centrifuges that powered the plant, slowly destroying them while feeding back information to the control center that said everything was functioning normally. It destroyed about 1/5 of the centrifuges in the Natanz nuclear facility, rendering them effectively useless.

Technical experts have traced the emergence of Stuxnet to engineering companies that supplied equipment to Natanz, meaning that these companies were infiltrated by operatives who hid Stuxnet in the equipment that was later sold to the Iranian government. Stuxnet’s code is remarkably sophisticated, and is said to be so complex that it must have taken years to write by a team of highly skilled professionals. Stuxnet is the first publicized instance of what is believed to be a successful cyber attack from one government to another, although neither the Americans nor the Israelis have officially taken credit for its creation.

Since infecting Natanz, Stuxnet has spread across the Internet and embedded itself in computers all around the world. The Stuxnet source code can be downloaded and modified by anyone with the knowledge, and can be used to target virtually any system that operates using industrial programmable logic controllers – such as water reservoirs, electrical plants, and other nuclear power plants. Stuxnet opened a Pandora’s box of cyberattacks on essential utilities, and now that the code and the ideas are out there, they’re here to stay.

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