Top 10 Most Dangerous Cyber Viruses to Date

Cyber viruses were looked at as nothing more than nuisances. However, they are responsible for damages that run in the billions today.

The interconnected world is forced to give cyber viruses the attention they deserve. Close to 400,000 new virus files are floating around the web, every day, and the cost of these mini-attacks exceeds $55 billion per year.

That said, in history, there was one cyber virus that was able to reach that amount, by itself, but we’ll touch on that further within the article.

10 Most Dangerous Cyber Viruses

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 computer virus attacks out there is immeasurable, and 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 computer 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 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 infected systems and 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 this 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 one percent of phishing emails. Which is fairly significant, when we consider that around 3.4 billion phishing emails are sent out each day.

Today, Mydoom is in its 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 created. Although a reward was offered for the developer of the virus, no one has been caught, to 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 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. 

3. ILOVEYOU

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 cyber 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 infection.

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 losses 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 it, 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 among 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 messages 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 computer virus infected close to 2 million servers worldwide, which is significant, when you consider that there are only 6 million IIS servers worldwide.

6. Melissa

Melissa was first encountered in March of 1999, spreading across the internet through emails and online forums, by offering free login details to adult sites.

Melissa was spread via a Microsoft Word document with a macro embedded into it. When unsuspecting PC owners opened this document, it would immediately run and infect the machine. However, this process only worked on systems that had macros enabled.

Melissa would infect only the first 50 contacts of a user’s Outlook address book. Machines that had been infected with it would thus, experience sluggish system performance, due to the mass mailings. 

The primary goal of this virus was to disturb networks by inundating them with tasks. The Melissa virus was able to propagate so fast, that it overwhelmed many email servers, shutting them down totally. Over 300 organizations were affected, worldwide. Reports, put the overall cost of this virus at around $80 million on money spent, recovering from the damages caused. 

7. Klez

Klez was first discovered in October 2001 and was a virus that took advantage of a known exploit in Microsoft Outlook at the time.

One of the most unique things about this virus was that it was polymorphic, which meant, it was capable of altering its code, to avoid detection. There were many variants of Klez, created by different cybercriminals – this simply made it more difficult to combat.

Klez infected over 7 million machines worldwide, resulting in damage costs running into the billions of dollars. 

8. Zeus

Zeus was a Trojan horse that was first detected in 2007. Its purpose was to steal sensitive financial data, such as login details and credit card numbers.

It worked by linking all infected machines into what’s called a botnet – which is a large network of infected machines. This botnet was then used to carry out attacks on major banking organizations and corporations.

Reports put the immediate financial costs at around $70 million, but that number could have run much higher when you consider the amount that went into recovery. 

9. Stuxnet

Stuxnet is a worm, which was first detected in 2010. It spread by corrupting USB drives and was used mainly for cyber warfare. Its main target was control systems such as industrial facilities and nuclear power stations. 

This virus was immensely powerful, capable of controlling nuclear centrifuges (such as in the case of Iran) causing real havoc. However, despite its many feats, it wasn’t nearly as destructive as many of the other major malware attacks.

However, it did show that it was possible to create a virus that could carry out major attacks on the most critical infrastructure of a nation. 

10. Sasser

This is another worm or virus that was created in 2004. Its main target was systems running on Windows XP and 2000.

It was able to spread by exploiting a known vulnerability in the Local Security Authority Subsystem Service of Windows. A service that is responsible for user logins. The result was millions of systems crashing out. This meant businesses were forced to shut down their networks until they were able to fish out and remove the infection.