Top 5 Worst Computer Viruses in History

Viruses have evolved a great deal, from the old days of personal computers, when viruses were created more recreationally than for real mayhem. Today, hacking can be seen as being a profession, with ambitions growing in line with that reality. Rather than viruses being created by hackers in a dank basement, hackers today are now a part of a much larger criminal underworld. Some of them may work for intelligence agencies or foreign governments. As the stakes continue to grow, so does the level of mayhem grow to match it.

1. Conficker Virus

This computer virus came out in 2009 and was able to infect millions of computers. It worked by creating a large botnet of remote systems, which were used to steal sensitive information, from where it could. Because of how complex the virus was, it made it rather difficult to stop. This led to a coalition of experts, working around the clock to stop it. At its height, it was able to infect millions of computers, which is how it earned the title “superbug”. Still, one of the most bewildering things about the virus, is that, up till now, most experts are still undecided about the actual intent of the virus. What it was supposed to do. The Conficker’s virus wasn’t used to do anything of real purpose, which is why it will forever remain a mystery.


This is amongst the most damaging viruses, listed amongst the first major virus of its kind. It was created by Reonel Ramones and Onel de Guzman, two Filipino programmers, and was able to infect millions of computers through email. It appeared as a love confession to unsuspecting victims. However, the moment the victim clicked on the attachment, it would immediately send itself out to everyone on the victim’s email list. As well as overwriting files on the victim’s computer, rendering it inoperable.

The virus would also make a copy of all the computer passwords, and send it back to the virus creators. This virus was a major catastrophe, especially for large corporations and governments. It spread to over 50 million computers, in a little over one week, causing the Pentagon, CIA and other large corporations to shut down their email systems. The total damage of this virus was estimated at over $10 billion.

3. Stuxnet

This virus was believed to be created by both the American and Israeli defense forces and was used to disrupt the nuclear program of Iran. It spread to host machines through infected USB drives and was able to run 20% of Iran’s nuclear centrifuges. If the system infected with the computer, had any Siemens software installed on it, the virus would cause the system to speed out of control, which would cause it to tear apart.

4. Zeus

There are literally millions of malicious files out there that target our personal affix, but Zeus stands out as the primary tool, that most of the world’s cybercriminals will go to when looking to carry out their own nefarious activities. It can be used for a wide variety of things, such as stealing passwords, including files, stealing identities, which in turn can be used to create an underground economy that can be bought and sold on the cheap. In today’s world, where online buying and banking online are the norm, a compromised identity means far more than it ever did in the past. All of these data, whether it be your date of birth, address, mother’s maiden name, security question, can be used to steal your wealth from you.

5. Sobig Worm (Sobig.F)

Sobig Worm came out in August of 2003 and infected Microsoft Windows computers, specifically. Sobig was much more than your typical worm, which would seek to replicate itself as much as possible, as it also had Trojan characteristics, in that it would attempt to mask itself. There were a number of variants of this virus, with the F variant being the most destructive. Sobig.F would typically get onto people’s computers through emails. These emails would have a number of subject lines, such as the following.

Re: Thank you!, Your details, “Re: Details,” and more. Due to the significantly large volume of emails tied to this virus that we’re able to be sent out, the worm was successful in bringing down traffic in Washington D.C, slowing down the systems of all the large corporations, and even grounding Air Canada. This virus infected over 2 million computers and caused around $37 billion in damages.

Author Bio:

Uchenna Ani-Okoye is a former IT Manager who now runs his own computer support website where he writes extensively on computer-related issues.

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