9 Most Deadly Computer Viruses Ever Discovered

Many of us at some point in time have had a Computer that starts acting very strangely. There are a lot of threats out there and many of them come in the form of computer viruses.

Computer viruses got its name because they act like biological viruses and replicates themselves and infect lots of files on a machine and can be spread to another machine just by doing stuff like sending files from one computer to someone else or using an infected USB Drive on another computer.

The World’s Most Dangerous Computer Viruses

We have Worms, Adware, Trojans and Rootkits which are hard to detect and can give attackers complete control of your machine
Perhaps even more frightening is Ransomware Attack where someone gets a hold of your data and sometimes sensitive data and makes you pay to get it back.


We’ll look at some of the biggest attacks on computers in this article.

> SQL Slammer / Sapphire Computer Virus

SQL slammer caused havoc in the USA in 2003. Slammer used an attack on one type of software but then infected machines would spread this worm through the net.



It mostly affected web-servers leading to bank ATMs crashing.

It messed with continental airlines’ electronic ticketing

It blocked 27 million people from the internet.

Seattle’s 911 services were affected.

The New York Times writes that what was so worried about this virus was its virulence because it infected 75,000 servers in just 10 minutes. It was stopped eventually by patches and antivirus software. But the creator of this virus is still unknown.


It also reappeared briefly in 2016 coming from IP addresses in the USA, China Mexico, Ukraine Vietnam, Russia, Venezuela, Argentina and Thailand.

It’s thought that it cost those who were hit by SQL Slammer all about 1 billion dollars.

> Melissa Computer Virus

Apparently the villain behind Melissa computer virus named it after an exotic dancer. It began as an infected Word document posted on an alt.sex Usenet Group.



If that was opened, It would send itself to 50 people on someone’s Microsoft Outlook email program

That might not sound too bad. But it created mayhem when emails were being sent at a rate that really messed with companies and big corporations so much so that in 1999 Microsoft shut down incoming email.

Users would get a message such as :

“Here is the document you asked for don’t show it to anyone else” and then there is an attachment with it.


According to one source, It cost people, governments and companies in all about 1.2 billion dollars.

Now anyone reading this article should know that you should never open attachments that look a bit sketchy.

But it seems back in those days people weren’t yet so tech-savvy

The creator of the virus was caught and sentenced to ten years in prison. But only served 20 months with a $5,000 fine

> Anna Kournikova Computer Virus

This computer virus was the brainchild of a 20-year-old Dutch guy named Jan DeWit.


He used the good-looking tennis player, Anna Kournikova as bait.


You basically would receive an email saying you had a photo of her. But if you clicked on the file it launched a viral visual basic script that meant everyone in your address book was forwarded the same thing this affected millions of people and overloaded servers all over the world this scared the young Jan DeWit as he didn’t think it would cause so much of a problem.

Sources said that by the time he understood what the worm did he had conferred with his parents and decided to turn himself in to the police.


Jan DeWit was lucky though and got away with just having to do 150 hours of community services.

> Sircam Computer Virus

This awful worm also made Microsoft Windows systems its target again.


It spread far and wide as it sent itself to people in your email address book.

You usually but not always saw the following message:

I sent you this file in order to have your advice.

The most clever thing about this computer virus is that it would choose random files from your computer and send them to others.


This was particularly bad for governments who don’t want random files being sent out.

It said it affected 12% of computers in North America and 11% of computers in Europe.


CNET confirmed that it cost 1 billion dollars in damages related to cleaning infected systems and to lost productivity.

No one has ever been arrested for creating this.

> Code Red Computer Virus

When your computers are infected with Code Red, Web pages that get affected suddenly get the message :

Welcome to worm.com hacked by Chinese.

Experts explain the HTTP requests exploit unknown buffer overflow vulnerability. Which allowed the worm to run onto the computer.


The malicious code is not saved as a file but is inserted and then run directly from memory.


It has been called one of the most advanced attacks ever that almost brought down the internet infecting Microsoft Internet Information Server.

Which many websites run on it was what is called a distributed denial of service attack. Which means overwhelming websites with too much traffic which brings them down.


Estimates on the damage caused by Code Red range in the billions.

According to the American Scientists it might not have been China who was the culprit though.

There were many investigations. But ultimately no one knows where it came from.

> Conficker Computer Virus

Conficker is one of the most costly infections.

It was discovered in 2008 and has in its lifetime infected as many as fifteen million computers.

computer virus
Credit: Emsisoft


It affected police departments in the UK as well as the military and really messed with their operations.

It infects Windows operating systems and it lasted a long time as it kept getting past patches and antivirus software.


Conficker is said to be the most destructive worm of all and it cost those infected around 9 Billion Dollars.

It’s a bit of a mystery to security experts, But they know it takes over a machine and then infects other machines in the network.

> ILoveYou Computer Virus

You have to love the name of this nasty computer virus, A bit like other things we have talked about it comes as an email with the words I love you in the subject line.


Well, that sounds nice. Isn’t it?


As so many businesses use outlook. It spread fast because folks open the attachment and once they did that everyone else in that address book got the same email.

Not only did it spread quickly, But it also deleted many of your files including every JPEG and mp3.

It reached 45 million people in one day in year 2000.

It was so big that Ford Motor Company shut down its email.

It was a little like Melissa, but it sent a mail to all your contacts and deleted personal files.

Even the Pentagon CIA and the British Parliament shut down their emails.


The virus was eventually linked to some young programmers in the Philippines.

It’s thought the cost of this virus was around fifteen billion dollars.

> Sobig Computer Virus

This happened in 2003 and included a worm and a Trojan horse all in one.

You’d get an email with any number of subject lines such as Re: Wicked Screensaver or Re: Approved.

If you click them there would be an attachment.


CNN wrote in 2003
So big dot F breaks virus speed record
It was said at the time to be the fastest-growing virus ever


It stopped Airlines from operating.

Slowed down many major corporations and worried the government. it mostly affected the USA.

A Cybersecurity expert wrote

At its peak, one out of 17 emails that we were processing were a copy of the SOBIG.F virus.

Certainly, we haven’t seen numbers like this before.

It is spreading at a very fast rate and the volumes are high in the USA. 40 million emails were scanned and half of them contained the virus.


It said it cost a massive 37.1 billion dollars.

> My Doom Computer Virus

You would get an email and if you open the attachment then your friends would be emailed. But because it also got into peer-to-peer sharing it spread fast.



It infected one in every 12 emails.

It spread via email and also via peer-to-peer file-sharing networks.

It was so big that Google was worried & offered a reward of $ 250,000 was offered to anyone who helped catch the perpetrators.


Some people say My Doom was the costliest virus of all time with an estimated 38 billion dollars in total damages in 2004.

People said it was someone in Russia. But that has never been proven.

Till today’s date My Doom is the greatest virus ever.


We hope this article helped you gain a lot of knowledge about the damage which a computer virus can cause. If you have any doubts about any of the above virus, Just drop a comment and our team will get back to you with a solution.

Also, as my recommendation, I would prefer you to buy a Quick Heal Total Security Antivirus to stay protected from all the computer virus.

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