Top 5 Most Dangerous Cyber Viruses to Date

Trista Jones  -  September 1, 2021  -  ,  

Once, they were looked at as nothing more than nuisances, however, today they are responsible for damages that run in the billions. The interconnected world is forced to give them the attention they deserve. Close to 400,000 new virus files are floating around the web, each and every day, and the cost of these mini-attacks exceeds $55 billion per year. That said, in history, there was one virus that was able to reach that amount, by itself, but we’ll touch on that further within the article.

This article will look at the most destructive viruses, primarily from a financial perspective. However, one thing to keep in mind is that the amount of virus attacks out there is immeasurable, that these are only the most notable. With around 130 million new malicious programs being introduced to the internet, each year, we can expect, in the coming years, for more significant viruses to emerge, and rightly take their place amongst the ones listed here. 

1. Mydoom

Mydoom is undoubtedly the worst virus attack in recorded history, when it struck, it caused around $38 billion in damages, by itself. When you adjust that figure for inflation, that’s around $50 billion. Mydoom is also known as Novarg, and is basically a worm virus that was spread through email. At its peak, the virus was responsible for a third of all emails that were sent around the world. 

Mydoom worked by scraping email addresses from the systems it had infected, then sending copies of itself using their addresses. It also linked all these infected systems together, into what is called a botnet, so that they could carry out DDoS attacks. The purpose of which was to target and shut down specific servers and websites. 

Mydoom hasn’t completely gone, there are still remnants of it today, accounting for around 1% of phishing emails. This is fairly significant when we consider that around 3.4 billion phishing emails are sent out each day. Today, Mydoom is in its own league, infecting unprotected systems all over the world, while sending out 1.2 billion copies of itself each year. That’s 17 years after it was originally created. 

Although a reward was offered for the developer of the virus, no one has been caught, till date. 

2. Stuxnet

From the information gathered, it was believed that the Stuxnet worm, was created in 2005, but it was first discovered in 2010. Its original purpose was to attack the nuclear facilities established by Iran. It worked by destroying the centrifuges within the facility, causing them to burn out. A company named Foolad Technic was its first causality, according to the log files found. 

Stuxnet was spread by Microsoft Windows and external storage devices, such as USB sticks. The primary target of the worm virus was to look for specific Programmable Logic Controllers (PLC), which were developed by Siemens. These are basically industrial control systems that run a plethora of automated processes, such as factory floors, chemical plants, nuclear power plants, and oil refineries. Computer systems effectively control these PLCs and they were the primary target of the virus. Reports state that the virus successfully infected over 50,000 Windows-based systems, and Siemens also reported that around 14 control systems within Germany were also infected. 


The ILOVEYOU virus was developed in the Philippines and immediately started to infect systems, around 2000. This virus also spread via emails, which contained the subject line ILOVEYOU, along with an attachment. The attachment had a filename similar to LOVE-LETTER-FOR-YOU.txt.vbs. If the end-user were to open the attachment, then it would run a Visual Basic script, which would infect the system. 

This virus wreaked havoc all over the world, costing the world around $10 billion in damages. It was believed that around 10% of all worldwide systems were infected with the virus. The situation got so bad at one point that large corporations and governments were forced to take their mailing systems offline, just to prevent their own infection.

In order to protect your system from a dangerous virus like ILOVEYOU, you’ll want to have a fairly robust internet security tool running on your computer. 

4. WannaCry 

WannaCry came out in 2017, and was/is ransomware, a virus that is designed to hijack a system, holding it to ransom. The WannaCry ransomware virus was able to infect systems in over 150 countries, causing significant loss in terms of productivity for businesses, government organizations, and hospitals. Companies and institutions that chose not to pay, were forced to rebuild their entire systems from nothing. 

Over 200,000 systems were infected with this virus, all over the world. However, this virus eventually came to an end when a security researcher figured out how to disable it. Computers that had dated operating systems were most affected by this virus. That’s the main reason why security experts recommend that you keep your system up-to-date. 

5. Code Red

Code Red was originally developed in 2001 and was first spotted by digital security employees of eEye. They named it Code Red, because the two security employees that discovered it, were drinking Code Red Mountain Dew at the time. 

The worm worked by targeting systems that had Microsoft IIS web server installed on them, exploiting a specific bugger overflow issue. It left next to no trace on the target machine, as it would run, almost entirely on memory, coming in at a measly 4 bytes in size. 

Once the virus had successfully infiltrated its target system, it would immediately begin to replicate, creating hundreds of copies of itself. This duplication process would increase to the point where it would begin to eat up system resources. 

Once it’d done that, it’d launch its own DDoS attack on several different IP addresses, the most notable amount them was the IP of the White House website. It also created backdoor access to different servers, allowing for remote access to its connected machines. 

One most notable message left behind by the virus, once it had successfully hacked your system was the “Hacked By Chinese” logo. After some time, a patch was created to counter it, but by that time, it had already cost companies $2 billion in damages. This virus infected close to 2 million servers worldwide, which is significant when you consider that there are only 6 million IIS servers worldwide. 


Uchenna Ani-Okoye is a former IT Manager who now runs his own computer support website https://www.compuchenna.co.uk 

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