These 5 Computer Viruses Were Really, Truly Awful

These days, the world’s scariest viruses often don’t always attack the human body. Some attack the digital infrastructure that we depend on for, well, just about everything. Computer viruses — and trojans, worms and other nasty pieces of malware — are the next frontier in global “health.”

Not all computer viruses are super-widespread or destructive. Some infect a few machines locally, then die out, go dormant or otherwise become inactive.

Some, though, wreak havoc across frighteningly wide geographies. Viruses have been responsible for some of the worst data breaches in history and have sapped untold billions of dollars from the global economy. Even the world’s best digital minds struggle to keep up with the relentless barrage of new digital treats.

There are plenty of contenders for “worst computer virus of all time,” but these five stand head and shoulders above the rest. Have you come face to face with any of these in your digital travels?

  1. Melissa

Named for a Florida stripper, Melissa actually wasn’t intended to cause havoc. Back in the late 1990s, when Internet pornography was still pretty novel, Melissa was conceived as a self-replicating file containing special passwords to nearly 100 adult websites. However, its self-replication capabilities proved overwhelming, and it quickly infected millions of machines across the United States — leading Microsoft to shut down its email servers for a time.

  1. My Doom

Unleashed in 2004, My Doom still holds the “world’s fastest-spreading virus” title. It ultimately infected 1 in 12 computers worldwide, a shocking total in any era, and forced Google to shut down for a full day. Worse, the authorities never caught the perpetrators. They could be working on their follow-up right now.

  1. Klez

2001’s Klez was the most sophisticated virus to date. It selected the optimal transmission method based on network and machine characteristics, and was one of the first viruses to effectively employ spoofing. Subsequent viruses copied many of its tricks.

  1. Nimda

Released in 2001, Nimda was one of the first viruses to affect cell phones (though, due to the low number of Internet-connected phones at the time, the damage was minimal). More notably, it affected backend systems across the web, throwing corporate operations into a cocked hat.

  1. SQL Slammer

SQL Slammer spread across the world in 2003, causing more than $1 billion in economic damages due to disrupted air travel systems, email servers and financial systems. It took Bank of America’s ATM network offline temporarily and caused Continental to cancel a handful of flights, disrupting thousands of travel plans.

No Rest for the Digital Weary

Sure as the sun rises, new digital threats will rear their ugly heads in the years to come. Some might make the malware described above seem quaint and mild by comparison. It’s critical for all Internet users, no matter how little they know about technology or how carefully they surf the Web, to stay vigilant. As the Boy Scouts say, “Always be prepared.”