It's the end of the world as we know it, and I feel fine..
Since the close of World War II, we have lived under varying degrees of fear regarding the possibility of a Nuclear or Biological war, where weapons could wipe out huge chunks of the world's population very quickly. In recent years the fear has shifted from a massive attack from a foreign superpower (i.e. the Soviet Union) to one lunatic dictator just sending off one or two towards places like London, Washington D.C., NYC etc. The nuclear menace has given way largely to the biological one, with recent epidemics of fear regarding anthrax powder in envelopes and packages being mailed around the world by terrorists (though I can't remember a single incident where it was actually anthrax and not just a generic white powder to scare people). We fear an attack that will kill millions quickly and almost silently.
Take a gander at the above animated gif. What you're looking at is the spread of a virus over a 24 hour period world-wide. By the end of the day, there are over 300k identified victims (and as a result vectors) for the virus. Remember, this is just one day... it's a virus that started in China and spread globally at an alarming rate. This happened on July 19th, 2001.
This is a before-and-after image of a different epidemic. This one is over a MUCH shorter time frame, only 30minutes. This took place on January 25th, 2003. Within 30min there were almost 75,000 identified infections.
You probably never heard about either of these incidents, they probably passed completely under your radar and were largely ignored by the media. That would be because these aren't human viruses, it's not a superflu, or a new strain of ebola... they're both computer viruses. Both particularly nasty ones that for a brief period of time partially crippled our worldwide communications grid.
The first animation is of the Code Red virus, which affected Microsoft IIS Servers that hadn't been properly patched up. The second was Slammer, a virus that hit unpatched Microsoft SQL Servers. Both spread extremely quickly and managed to take down very important pieces of the Internet. In the case of Slammer, the spread was so fast that several of the root DNS servers (the master servers that keep a record of all domains and IP ranges) were flooded offline for a portion of the day, rendering large chunks of the Internet unreachable.
Thankfully, neither did much serious damage to infected machines, they just used them to spread to other vulnerable machines. Despite their relatively "safe" payload, they still managed to wreak havoc with the core components of our society.
If you think about it, The Internet is the backbone to everything we do. Companies depend on it. The government depends on it. It is how we manage shipping, ordering, how we coordinate with one another, how we communicate and do day to day business. Every moment of your life is now pretty much connected to this vast global communications network. What happens when that network fails? Thankfully, Slammer hit on a weekend, minimizing potential damage, and Code Red didn't spread fast enough to pose a really serious problem to the core servers. But in both cases we saw the aftermath of what a virus could do. Companies lost millions, communication between individuals, companies, and governments were disrupted.
It's now said that a clean machine, when placed online, will become infected within an average of 3min. That's not even long enough to download and apply patches.
It's already starting, the weapons for the next great conflict are being built... but they're coming from teens in Europe, Asia, the Midwest USA, everywhere. It's only a matter of time before someone tries to harness them and use them in an intentional attack. So far they've mostly just been "proof of concept" works, pieces of code to just show it could be done. How long before the payload is actually dangerous? You don't need to attack with bombs and germs anymore, you can do more damage to your enemies by cutting them off from their lines of communication, render them silent and cripple their economy.
Soon we'll live in a world where a kid with a keyboard is more dangerous than a whacko in Asia with a nuke. A nuke can hit one target and one target only... a computer virus can hit the whole world.