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Top 10 deadliest computer viruses recorded in history.

Visitors have accessed this post 346 times.

There will be a negative side to all things in the world. Viruses are one of the most important issues in the age of technology. The age of programmers has begun since Ada Augusta Lovelace wrote the first program. Although there are many good programs that can be used, computer viruses are programs that are designed to do some wrong things without a trace.


The 1st Personal Computer virus began infecting 5.2’’ floppy disks in 1986. As Securelist reports says it was the work of two brothers, Basit & Amjath Farooq Alvi, who ran a computer store in Pakistan. Here, we can get some Ideas about the deadliest computer viruses.

1.    Melissa

Melissa was a Mass-Mailing macro virus released around 26th March 1999. It was released by David L. Smith. This virus (An Infected Word document) posted online, claiming to be a list of passwords to adult websites. Once anyone opened it, it would mail itself to the users mail contacts. It slowed down the email system due to overloading Microsoft Outlook & Microsoft Exchange servers with emails. The U.S. FBI estimated cleanup and repair costs at $80 Millions.

2.    I Love You Virus

I Love You, Lovebug or love letter for you is a computer worm that infected over 10 million Windows Personal Computers on 4 May 2000. This worm reached users via Email. In just 10 days, this worm reached an estimated 45 million users and caused almost $10 Billion worth of damages. It has been believed that this virus impacted at least 10% of the internet connected Personal Computers in the world.


I Love You was created by a 24 years old Onel de Guzman who was a college student in Manila, Philippines. He was a poor student, and he wrote this virus to steal user passwords. So he could login and use online services without paying any fees. But the funny thing is, He reportedly had no idea how far his creation would spread.

3.    Sasser

Sasser is also a computer worm that affects Personal Computers running vulnerable versions of the Microsoft Operating System such as Windows XP and Windows 2000. This worm spreads by exploiting the operating system through a vulnerable network port.

Sasser was discovered on 30th April 2004. It was created by an 18 years old student called Sven Jaschan from Rotenburg. Later, he was arrested and after a $250,000 bounty was posted for the computer virus creator. Sasser crashed millions of Personal Computers. It caused almost $500 Millions of damage.

4.    Code Red

Code Red was a computer worm which was observed on the internet on July 15, 2001. It was a server jamming worm, and it attacked computers running Microsoft’s IIS web server. It penetrated about 975,000 hosts and displayed the words “Hacked by Chinese!”. Furthermore, it caused almost $2.4 billion of damage. This virus infected Personal Computers and Distributed Denial of Service (DDoS) attacks on the U.S. White House’s website. In fact, the White House had to change the IP to defend against this attack.

5.    Klez

Kelz is the most destructive worm in history. It first appeared in October 2001 and originated in China. Klez infects Microsoft Windows systems, exploiting vulnerability in Internet Explorer. It caused about $19.8 Billions in damage

6.    MyDoom

MyDoom is a Computer worm affecting Personal Computers with Microsoft Windows. It was first discovered on 26th of January 2004. It was Identified as the Worst computer virus outbreak. Likewise, it was one of the fastest spreading viruses of all time. MyDoom caused estimated damage to $38.5 billions in 2004. MyDoom’s aim was to takedown websites like Google and Lycos. It managed to take out Google for almost a day.


7.    Slammer

Slammer or SQL Slammer is a computer worm discovered in 2004, that causes Denial of Service (DoS) attacks on some Internet hosts and slows general Internet traffic. It infected most of its 75,000 victims within 10 Minutes. Across 200,000 Personal Computers users were infected by Slammer. Slammer cost an estimated $750 Million.


8.    Zeus

Zeus or Zbot is a Trojan Horse Malware that runs on versions of Microsoft Windows. It is an online theft tool that hit the web in 2007. Zeus targeted Windows Personal Computers to perform criminal acts. The most common of these tasks are Man-In-The-Middle attack, browser keylogging and form grabbing. It infected targets via phishing scams or downloads. Estimated that the malware infected about 3.6 million Personal Computers in the U.S. in 2009. It managed to compromise thousands of FTP accounts and computers from The Largest corporations and banks like Oracle, Amazon, Bank of America, Cisco, etc.

Zeus causes documented damage to $100 Million but undocumented theft and damages are undoubtedly much higher.

9.    Stuxnet

Stuxnet is a Malicious computer worm first identified by VirusBlokAda in 2010. Stuxnet was originally aimed at Iran’s nuclear facilities. It was created by Equation Group. It was mostly infected with various versions of Microsoft Operating systems. This worm infected over 200,00 computers and caused 1000 machines to physically degrade.


10.    CryptoLocker

CryptoLocker Ransomware attacks occurred between 5th of September 2013, and late May 2014. It was reported as the first ransomware attack. It was identified as a Trojan Virus that targeted computers running Microsoft Windows. This Virus encrypted files on hard drives. The only way to decrypt the files was to pay a ransom by the certain deadline.

Law enforcement managed to stop the Ransom operation, but unfortunately about $27 Millions of ransom was already paid.


Here are some notable viruses for your knowledge.

·        Sircam: Sircam is a Mass-Mailer computer worm that was first identified in 2001 by email in Microsoft Windows system. It targeted computers running on Microsoft Windows 95, Windows 98 and Windows Me. It originated in Mexico. Reportedly it caused $3 billion worthed damages.

·        Yaha: Yaha is an Email worm discovered on 15th February 2002. It was created by Hirosh from Kerala, India. It targeted Microsoft Windows Personal Computers. Not only that, but it caused about $11.5 billion worth of damages.

·        Swen: Swen is a Mass-mailing computer worm written in C++. Experts believe that Slovakian programmer created this worm. It was discovered on 18th September 2003. Its financial cost has been pegged at $10.4 billion.

·        Mimail: Mimail is an email worm that used to harvest passwords from victims. It originated in Russian and was first discovered on 1st of August 2003. It targeted Microsoft Windows systems. Reportedly it caused $11.5 billion worth of damages.

·        Storm Worm: It is a phishing backdoor Trojan horse that infects Personal Computers using Microsoft Operating System. It was discovered on 17th January 2007. It attacked Millions of Personal Computers with an email about approaching bad weather (“230 dead as storm batters Europe”).

·        Conficker: It is a computer worm targeting the Microsoft Windows Operating System. It was first detected in November 2008. It was used to steal Administrator Passwords and other credentials. Conficker infected Millions of Computers over 190 countries.

·        Flashback: It’s a Trojan Horse which targeted Personal Computers running Mac OS X. It was discovered in September 2011 by Intego (an Antivirus Company). Flashback infected more than 650,000 MAC Personal Computers around the world.

·        WannaCry: It was a worldwide cyberattack in May 2017 by WannaCry Ransomware. It was ripped via computers in 150 countries, and it caused massive productivity losses.

·        Colonial Pipeline Ransomware attack: It is one of the largest virus attacks that happened on 7th May 2021. This Ransomware that mainly targeted an American oil pipeline called Colonial Pipeline system that originated in Houston, Texas. That oil company paid about $4.4 million dollars in Bitcoin. Fortunately, US law enforcement was able to recover the Ransom payment. The FBI traced the money by monitoring cryptocurrency movement in digital wallets, but unfortunately it became harder to find the actual hackers behind this attack.


Some of these viruses are still alive and make some minor damages continuously. From my personal experience, I lost almost 8GBs of my favorite songs and other project files because of a virus like this. That is not a big deal, but most of the people lost their money or even equipment. According to a recent study, CyberSecurity ventures expected global cybercrime costs to grow by 15% per annum over next 5 years, reaching $10.5 trillion annually by 2025, up from $3 trillion in 2015. In 2021, about $6 trillion worth of damages happened because of cybercrime and experts are expecting about $8 trillion by 2022.


These days we have more technologies and gadgets, but still hackers and other cyber criminals use these computer viruses to do illegal activities. So we must be careful with our Personal Computers.


We can identify viruses with some activities happening in the system.

Repeated error messages, unexpected shutdowns, and the computer suddenly slowing down, New Toolbars or shortcuts that we didn’t add, Rapidly draining battery, are some signs that could mean the system is infected. If you see more than one of these signs, you must check for viruses.


Using Antivirus, using a Strong firewall, Install a popup blocker, beware of email phishing scams, educate knowledge to our family, friends and colleagues are some prevention tips.


We should use Antivirus programs to add security to our system. It will easily detect and block unwanted programs like viruses which try to penetrate the system.

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