10 Deadliest Computer Viruses of All Time

The increasing use of technology has created new challenges for companies and businesses. IT experts and cybersecurity professionals are coming up with new ways to prevent cybersecurity threats. Tech users are bound to come across computer viruses at some point. For instance, if you see an unknown software along with your internet installation package, call Spectrum if you are a subscriber or if you are seeking Spectrum internet services and installation for more information.

Most of us have come across computer viruses at some point in our lives. Many might see computer viruses as a mild inconvenience. In some instances, however, viruses can completely wipe out sensitive information from a network or system. This is one of the major concerns for tech companies and businesses around the world.

This article explains some of the deadliest viruses that completely crippled the tech infrastructure and caused billions of dollars’ worth of loss to the companies they targeted. Keep reading to know the complete list of the top 10 deadliest computer viruses of all time.


MacBooks are known for their powerful security features. The macOS contains built-in security features that make it nearly impossible for viruses to access the system. The keyword here is nearly impossible. That means even the mighty macOS is immune to viruses. The first instance of a Trojan affecting macOS was reported in 2011.

Intego discovered the Trojan called Flashback that had infected more than 0.6 million MacBooks. The malware in question faked itself as a flash install and gained access to hundreds of thousands of MacBooks. Apple later came with an update that removed Flashback from the operating system of infected MacBooks.


Hackers came up with this particular Trojan horse ransomware to target Windows laptops. CryptoLocker used multiple methods such as email to spread itself on target computers. Despite getting the ransomware removed, IT experts were unable to eliminate it. In the end, the joint efforts of law enforcement and cyber companies saved the day.

It is said that the hacking group responsible for the attack received $3 million from affectees. Officials arrested the group’s leader Evgeniy Bogachev who provided them with the encryption keys. Moreover, CryptoLocker infected as many as half a million computer systems. Before Bogachev’s arrest, the only way to put away the virus was to pay the ransom.


The name for the malware speaks for the destruction it caused. The email worm first appeared in 2004 and infected Windows computers. It became one of the fastest spreading malware since ILOVEYOU. It appeared as an email transmission error and provided remote access to the creators. Mydoom caused approximately $38.5 billion in damages.


Stuxnet served the purpose of cyberwarfare. It is said that the US and Israeli governments worked together to create the virus for the sole purpose of ruining Iran’s nuclear program. It targeted the Siemens network and successfully disrupted Iran’s nuclear centrifuges.

Its programming allows it to take down automation processes such as the Industrial Programmable Logic Controllers (PLC) used in nuclear works. Stuxnet primarily targeted systems created by Siemens. The company eventually came up with a way to remove the worm from their systems.


Conficker emerged in 2008 to target Windows OS. This particular worm identified flaws in the operating system and created a botnet to infect it. Conficker successfully ruined more than nine million computers across the globe. That included systems under the use of individuals, businesses, and government agencies. Also, the monetary damages were no less than $9 billion.


Zeus is arguably one of the deadliest viruses on the list. It appeared in 2009 and targeted hundreds of multinational corporations and banks across the globe. It performed form grabbing and man-in-the-browser keylogging among other criminal tasks.

Several big names including Cisco, Oracle, Amazon, and Bank of America became the targets of Zeus. It infected more than one million computers in the U.S. alone. Also, the ring behind the virus stole approximately $70 million from the networks and computers it targeted.


Sasse emerged in 2004 and disrupted over one million computer systems. It also caused $18 billion in damages. The most startling part, the virus was created by a student named Sven Jaschan; creator of the NetSky worm. Sasser disrupted the critical infrastructure of millions of computers around the world.


Melissa disguised itself as a word document containing passwords for explicit content. It entered the mailbox of users mentioned in the creator’s email address. It ruined millions of computers and caused up to $80 million in damages.

Code Red

Code Red infected more than two million servers and resulted in the loss of $2 billion for the systems that were targeted. It first emerged in 2001.


The most infamous virus of all time happens to have the sweetest name. It damaged 10% of the world’s IT network and caused billions of dollars’ worth of damages.

Leave a Comment