Viruses are destructive computer codes that have the ability to seriously destroy computer systems, resulting in loss of data, system failure, and security threats. The first computer virus was identified in 1971, and ever since then, malwares have continued to advance over the years, becoming increasingly more dangerous and complex.
Let’s dive in and take a closer look at the 10 most deadly viruses that left a permanent mark on the online world.
1. The Love Letter That Started a Digital Pandemic: The Love Letter That Started a Digital Pandemic: I LOVE YOU, a well-known virus that was first discovered in May 2000, distributed its dangerous script via emails with the subject “I LOVE YOU” disguised as a heartfelt message. A malicious script called “LOVE-LETTER-FOR-YOU.txt.vbs” was attached to the email and was successful in stealing passwords, overwriting files, and automatically distributing the infected script to all of the victim’s stored addresses. Out of the 10% of all personal computers linked to the internet at the time, the virus propagated at an unparalleled rate, infecting 50 million machines. Due to file destruction, company interruption, and data recovery costs, the attack caused significant damage with estimated losses of between $10 billion and $15 billion. Due to inadequate cybercrime laws, the virus’s origin was traced back to Filipino programmers, who were not prosecuted.
2. The Ransomware That Held the World Hostage, WannaCry (2017): When WannaCry launched its attack in May 2017, it was based on a Microsoft Windows vulnerability that the hacker collective Shadow Brokers had discovered. This malware demanded 300-300–600 Bitcoin payments to lock down compromised computer files. WannaCry was deadly due to its automatic spread capacity, since it infected over 200,000 workstations across 150 countries, including government, banking, and medical organizations. Numerous operations were canceled, and emergency transport services had to be diverted as a result of the WannaCry attack on the National Health Service (NHS) in the United Kingdom. Fortunately, a researcher discovered a patch in the code that served as a “kill switch” for the malware, slowing its spread even though $4 billion worth of harm had already been done.
3. My Doom (2004): The Email Worm That Spreads the Fastest When MyDoom first surfaced in 2004, it was the fastest-spreading email worm in history. The subjects “Error” and “Mail Delivery System” or “Test” made the emails that users received appear authentic, but the attachments were malicious. Once activated, the malware turned computers into spam-sending machines that launched distributed denial-of-service attacks on well-known websites like Microsoft and Google at the same time. Millions of PCs were infected by MyDoom, which resulted in a 10% decrease in internet speed globally and $38 billion in market losses. Despite a great deal of research, the person who created this software has not been identified.
4. Code Red (2001): In 2001, Code Red made an appearance as the worm that tried to attack the White House. Because it exploited a vulnerability in 2001 to attack Microsoft’s IIS web servers, the Code Red worm got its name from the Mountain Dew Code Red. Because it attacked servers with weaknesses on its own, this virus functioned differently than typical malware. Before it led websites to show the defacement message, “Hacked by Chinese!” Code Red was able to infect over a million PCs. Before authorities changed the site’s IP address to protect it, wind machines threatened to conduct a DDoS attack on the White House website. Microsoft released an urgent software upgrade as a result of the widespread public panic caused by the worm outbreak. The costs of the cleanup and missed output came to more than $2 billion.
5. Zeus: The banking Trojan Zeus (2007) was successful in robbing victims of millions of dollars. Zeus (Zbot), a banking Trojan, first surfaced in 2007 with the primary objective of stealing credentials using real-time form retrieval and keylogging. Malicious downloads and phishing email campaigns were the main causes of the infection that spread to millions of systems. Zeus gained access to a computer system and then used it to drain online bank funds, causing $100 million in damages to both personal and business accounts. By acquiring it for various harmful actions, cybercriminals might gain access to its botnet. Key components of the Zeus network were shut down by the FBI in Operation Tovar (2014); however, the software is still in use today.
6. Stuxnet (2010): According to the world’s first digital weapon security experts, Stuxnet was a government-sponsored cyberweapon developed by Israeli and American scientists to target Iranian nuclear installations. USB drives containing code that exploited zero-day vulnerabilities in Windows operating systems were used by the virus to spread. Stuxnet caused uncontrollable centrifuge malfunctions at Iran’s uranium enrichment plant in Natanz, which ultimately resulted in their destruction and caused a multi-year delay in the development of Iran’s nuclear program. The virus was discovered after its intended target began to infect systems all around the world. Because Stuxnet proved that computer viruses could cause physical devastation, it marked a turning point in cyberwarfare.
7. The Ransomware That Started a Trend: CryptoLocker (2013) Modern ransomware was developed as a result of the CryptoLocker ransomware virus, which encrypted victim files using Bitcoin cryptocurrency and prepaid cash vouchers. Through malicious ads and email attachments, CryptoLocker spread its influence, infecting hundreds of thousands of PCs. If victims did not pay within 72 hours, all of their files were permanently erased. Before authorities removed its control servers through Operation Tovar, the attackers wanted a ransom of $3 million. Ransomware is currently one of the biggest online hazards facing internet users because of the countless imitation programs that have been created since CryptoLocker first surfaced in 2013.
8. Conficker (2008): The Enormous Botnet-Building Worm Conficker (Downadup) was introduced in 2008 when it found flaws in Windows systems to create one of the largest botnets ever seen. The attack recruited new malware through its download routines, blocked security upgrades, and stole credentials. Conficker’s influence peaked when it infected over 9 million systems, targeting military networks, hospitals, and government institutions. Microsoft offered $250,000 in an attempt to apprehend the developers, but they were unsuccessful. Although improved cybersecurity procedures were brought about by the worm, some Conficker components are still accessible online.
9. Melissa (1999) – The Virus That Crashed Email Servers: Melissa, the first mass-mailing macro virus, got its name from a stripper in Florida. Users contracted the infection when they opened Word documents that were shared on online discussion boards and contained password-related knowledge. When it was opened, it sent an email to the first fifty individuals in the victim’s Outlook contacts list. Due to the overwhelming volume of emails, server capacity was so severely harmed that large companies like Microsoft and Intel joined many others in completely ceasing to provide email services. The Melissa virus caused $80 million in damages and was the first well-known instance in which a virus writer, David L. Smith, was sentenced to 20 months in prison.
10. The Worm That Shut Down the Internet for a Day: Slammer (2003):The SQL Slammer worm, which exploited Microsoft SQL Server buffer overflow vulnerabilities, propagated at an extraordinary rate in January 2003. The Slammer worm gradually infected over 75,000 systems in ten minutes, with the number of infected servers doubling every 8.5 seconds. Widespread Slammer traffic interrupted airline check-ins, bank ATMs, and 911 emergency services and caused delays in internet connections worldwide. Although the worm itself did not erase any data, its denial-of-service capacity caused $1.2 billion in damage. When Microsoft released a patch six months prior, yet many PCs were still without the update, the significance of deploying software fixes became immediately apparent.
