Top 12 Worst Computer Viruses in History

Ali Qamar  - Cybersecurity Analyst
Last updated: January 15, 2024
Read time: 18 minutes
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These 12 worst computer viruses have generated billions of dollars via stealth malicious activities.

THE TAKEAWAYS

With the advent of the first online virus in 1986, millions of computer viruses and worms infect computers daily, posing a severe threat to netizens’ online security. Such malware attacks are, so far, the most valuable tools of cybercriminals that can efficiently cause financial losses to the victim. This article lists the worst computer viruses in history that are still famous for their devastating damages.

Since 1986, many harmless or harmful malware have emerged and disappeared as cybersecurity people learned to cope with them. Nonetheless, a few of these are known for being the worst computer worm attacks in computer security history.

This article tells you about the top 12 worst computer viruses to hit the digital arena. Furthermore, these viruses are all ranked according to the extent of financial damage they inflicted on the world. Hence, while they might not look so sophisticated, they undoubtedly proved to be the most successful viruses for cybercriminals.

Quick list of the worst computer viruses

Here is a summary of the worst computer viruses in history

  1. Mydoom (38 billion): It caused an estimated $38 billion in damage and was responsible for a quarter of the world’s email traffic. Although it still exists, it’s behind only 1% of the world’s phishing emails.
  2. Sobig (30 billion): A worm in 2003 caused about 30 billion USD in damages and disrupted many businesses worldwide, including Air Canada.
  3. Klez (19.9 billion): It appeared in 2001, infected 7.2% of all PCs, sent fake emails, and evolved into more dangerous iterations over the years.
  4. Iloveyou (15 billion): It disguised itself as a plain text file in love letters and sent copies of itself to every contact in the infected computer’s email list.