Top 10 Computer Viruses of all Time with Shocking Devastation

Once upon a time, a computer virus was considered funny. Now, it’s so serious that it has the potential to cost billions of dollars in damage. Annually, more than 350,000 new pieces of malware are discovered every day and the sad part is, this is just the tip of the iceberg. Here are the top 10 computer viruses that have cost severe damage.

10. CryptoLocker

Top 10 Computer Viruses
Business Insider

The CryptoLocker ransomware virus managed to attack 250,000 computers by encrypting the files. To make matters worse, it displayed a red ransom note that informed users “your important files encryption produced on this computer.” As soon as the message is displayed, a payment window pops up accompanied by the note. The creator sends copies of the CryptoLocker virus by using Gameover Zeus botnet. It is estimated that CryptoLocker extorted from its victims $3,000,000.

9. Sasser

Top 10 Computer Viruses
Source: F-Secure

Sasser was written by Sven Jaschan, a 17-year old German computer student. In 2004, he was arrested at the age of 18 after a $250,000 bounty was posted for him. The authorities gave him a suspended sentence after they discovered he was a minor. This virus crashed millions of computers and some reports claim that the overall damage was $18 billion. However, that is simply not true as the low infection rate indicates the damage being closer to $500 million.

8. Slammer

Top 10 Computer Viruses
Source: F-Secure

Slammer came out in 2003 and cost an estimate of $750 million when it hit 200,000 computers. This virus attacks and exploits vulnerable IP addresses. It then sends itself to other machines. These machines were then used to launch a DDoS attack on several internet hosts. This slowed down internet traffic. The virus hit banks and crashed ATM machines, making it difficult for customers to access their money. The virus hit again in 2016 in China and Mexico. Globally, the virus cost an estimated $1.2 billion.

7. Code Red

Top 10 Computer Viruses
Source: CyberReason

Code Red was named after the Mountain Dew drink. It broke out in July 2001 and infected almost 360,000 computers in a day. The infection was very difficult to stop because it had the ability of coming back and reinfecting a computer that had just been cleaned. It hit Microsoft IS servers and caused massive service problems that took days to cleanout. This virus cost the world almost $2.4 billion.

6. Nimda

Source: CBS news

Nimda comes from the word “admin” spelled in reverse. It infected both workstations and servers running Windows software, employing a wide range of tactics to spread, including by email, browsing compromised websites, and exploitation of known vulnerabilities. The Nimda outbreak occurred in September 2001 and as a result of Nimda’s various distribution tactics, spread throughout the world in just one hour. The economic damage of Nimda surpassed previous viruses such as Code Red.

5. Zeus

Source: PCRisk

Zeus hit the web in 2007 and caused havoc. A whitepaper estimated that it caused 44% of all banking malware attacks. It breached the privacy of 88% of Fortune 500 companies hitting 2500 organizations in all, with an infection total of 76,000 computers in 196 countries. It started in Eastern Europe and resulted in damage of $3.7 billion. That’s a pretty large sum, wouldn’t you say?


Source: TechTimes

According to Golden Richard III, the ILOVEYOU virus, or Love Bug, caused massive financial damage and resulted in millions of computers becoming infected. The virus disguised itself in an email with a love letter from one of the user’s contacts. When the unsuspecting user opened the love letter, the virus would proceed to inflict damage on the machine and spread to all the users contacts. In May 2000, it is estimated that the ILOVEYOU virus infected 10% of the internet-connected computers in its first 10 days, causing the CIA and Pentagon to shut down their computers for a while. It is estimated to have cost up to $15 billion to remove.

3. Klez

Source: F-Secure

Klez surfaced in October 2001 at a cost of $20 billion in damages by spreading private information. Klez infected 7 million PCs, which was 7.2% of all computers through fake emails spoofed with a recognized sender. Several Klez variants have since been discovered infecting files by copying itself.

2. Sobig

Source: F-Secure

The Sobig virus was spread through several variations named Sobig.A through Sobig.F from January to August of 2003 throughout Canada, Europe, Asia, and the UK. Sobig interfered with many business and even disrupted Air Canada ticketing with an estimated cost of $30 billion. Despite a reward from Microsoft announced in November of 2003, the creator of the Sobig virus has not been caught.

1. MyDoom

Source: Comodo

You may remember hearing about the MyDoom virus. The MyDoom virus resulted in damage of $38 billion after its outbreak in 2004. It took email addresses from infected machines and then sent itself to those addresses. At the time it was the fastest spreading email virus ever infecting 1 in 12 emails at its peak. The worst part is that MyDoom is still around today and is responsible for 1% of all phishing emails, or 3.4 billion phishing emails per day, with the developer still at large with a $250,000 bounty.

Last Thoughts

While most of these viruses are no longer a threat, there are new computer viruses every day. Thankfully computers have also come a long way in preventing viruses. Still, the best advice is to simply avoid opening or downloading anything that you aren’t sure who it’s from.