Computer viruses – no one likes them. No one wants to deal with them. But yet, somewhere someone is always writing them. Well, it keeps the virus scanner companies in business at least.

Being in IT I have dealt with my share of viruses. I remember the last 4 on this list. At least 2 of those kept us tecnicians running around like chickens with our heads cut off. I often fantasize about getting the virus coders all in a room together, and…. Oh, no violence right?

Anyway, reminisce with us as you read over this list. Do you remember any of these? Were you directly affected? Did you have to rebuild a computer?

Computer security experts say that every day there are more than 100 computer viruses unleashed and disseminated via the web. Below is a list of eight of the worst computer viruses and worms in the history of the internet.

1971 Creeper Virus

It’s debatable, but some people claim this was the first computer virus. The virus was discovered on a military computer network that served as a prototype to the internet we enjoy today. An infected computer would display a message saying: “I’M THE CREEPER: CATCH ME IF YOU CAN.” Though mostly harmless, the virus independently gained access to a computer through the modem and copied itself to the system.

1982 Elk Cloner Virus

The Elk Cloner virus, one of the first viruses known to spread in the wild, infected the boot sector of Apple II floppies. When an infected computer was booted from a floppy disk, the virus would run and copy itself to any uninfected floppy disk it could access. Most computers of this era had dual floppy drives and many people shared floppy disks, so the virus was replicated a lot. Unlike present-day viruses the Elk Cloner wasn’t created to be destructive or criminal it was more of a practical joke. The 50th time an infected computer booted up the code would display a message that said:

“Elk Cloner:  The program with a personality

It will get on all your disks
It will infiltrate your chips
Yes it's Cloner!

It will stick to you like glue
It will modify ram too
Send in the Cloner!”

1988 Morris Internet Worm

This worm was created to do nothing – at least nothing visible – and is considered to be the grandfather of computer worms. The purpose of the Morris Internet Worm was to spread itself to as many computers as possible without any detection. However, the code of the worm was flawed, which caused the computer system to slow down as the worm made more and more copies of itself on the system. The worm spread at a surprisingly quick rate and showed that this level of connection and replication was possible.

1999 Melissa Virus

Many people remember the Melissa virus because it spread cleverly via e-mail. The Word macro virus would send e-mails from the infected computer users’ address book. Microsoft, Lucent and Intel actually had to temporarily shut down their e-mail servers because the virus was generating such large amounts of dummy e-mails that their systems were getting clogged. Again, this wasn’t a virus designed to be destructive, it just gummed up the server works.

2000 ILOVEYOU Virus

This virus was one of the fastest spreading viruses of all time. The virus spread via e-mail (as an attachment) from a ‘friend’ in the users’ contact list; however this ‘love letter’ infected computers across the globe. The virus downloaded an application to the computer that stole passwords and personal data, causing about $10 billion in damages.

2001 Code Red Virus

Code Red launched a denial of service attack, taking advantaged of Windows 2000 and Windows NT operating systems vulnerabilities. This virus actually initiated a DDos (distributed denial of service) attack on the White House by overloading their servers, causing them to be unable to perform needed tasks.

2003 SQL Slammer Virus

The SQL Slammer was a small, rapidly spreading virus that infected some of the most-used web servers and caused numerous problems across the U.S. Also known as Sapphire, the virus caused outages in 911 service in Seattle, forced Continental Airlines to cancel flights because of electronic issues and crashed ATM services for Bank of America. It’s estimated the Slammer caused about $1 billion in damages.

2007 Conficker Worm

This virus caused more than $9 billion in damages and infected millions of computers all over the planet. Conficker downloaded and installed malicious software to computer systems from sites controlled by hackers. The hackers then logged keystrokes in order to remotely control the infected PCs.

To ensure your system is protected from viruses like the ones listed above and new malware, remember that nothing you do online is private – hackers can follow your every online move. Don’t visit rogue sites, don’t download programs from untrusted sources and don’t click blindly around the internet. Be smart and aware online and know that if something ‘feels’ wrong, it most likely is.


Emilia Fielding has been contributing to websites and blogs since 1999. She writes a disturbing amount about antivirus software and is pleased to be able to use her powers for good rather than evil. For now.