12 Days of Computer Viruses

12 Days of Computer Viruses

Computer viruses have been around as long as computers themselves. But with the vast majority of the globe and its data now being connected to the World Wide Web, the potential scale of havoc reeked by these cyber threats is growing larger by the day. So, in keeping with the season, here are 12 such viruses, worms and Trojans to have made their way into our digital lives.


Often referred to as the first worm in history to be distributed via the Internet, Morris caused an estimated US$100,000 – 10,000,000 worth of damage. Its creator was student Robert Tappan Morris, who became the first person to be convicted under the country’s 1986 Computer Fraud and Abuse Act.


Cernhobyl was the most destructive computer virus the world had ever seen when it struck. Not only did it erase the hard drive, it would also wipe out the flash ROM BIOS of the computer.

MELISSA (1999)

Named after an exotic dancer from Florida, Melissa was the first major virus to spread via email and marked the beginning of the Internet virus era. Though relatively harmless, it still brought whole organizations to a standstill, simply by filling their inboxes.


Designed to steal Internet passwords, the ILOVEYOU virus worked by unleashing a malicious program that accessed users’ image files. It caused around $15 billion worth of damage.

CODE RED (2001)

Code Red was a virus that notoriously managed to deface and take down the whitehouse.gov website, forcing other government agencies to take down their public sites as well.

KLEZ (2001)

Raising the bar once more, this virus had many different versions, some of which could render computers inoperable. Not only could it act as a normal computer virus, worm or Trojan, it could disable virus protection software and even pose as a virus-removal tool.

NIMDA (2001)

The purpose of this virus was to slow Internet traffic to a crawl. It spread across multiple servers in record time, topping the list of reported attacks within 22 minutes of hitting the Internet. Around 1 million computers were infected.

SLAMMER, a.k.a. SAPPHIRE (2003)

Sometimes referred to as Sapphire, Slammer was an Internet worm that doubled in size every 8.5 seconds. Its victims included the Bank of America’s ATMs, Continental Airlines, a 911 emergency response system and a nuclear plant in Ohio.

SOBIG.F (2003)

This virus lived up to its name, bringing freight and computer traffic in Washington D.C to a halt, as well as briefly grounding Air Canada. The total damage was around $37 billion.

MYDOOM (2004)

Another fast-spreading virus via email, MyDoom infected around 2 million computers and caused a staggering $38 billion worth of damages.

LEAP-A, a.k.a OOMPA-A (2006)

Whilst significantly less at risk, Macs are by no means immune to virus attacks. Leap-A proved this, by using the iChat instant messaging program to infiltrate and spread across vulnerable Mac computers.


After taking on thousands of reincarnations, Storm Worm became the biggest botnet in the world. At one was believed that around 15 million computers were infected simultaneously and all within control of the criminal underworld.

ITC Security can help you to protect your company network from harmful viruses and data leaks. We also offer security and network consultancy services, amongst many others. Contact us to find out how you could benefit.