Forms of electronic terrorism
XTC46,
I think that you can divide electronic terrorism into many different forms, so of them more serious than others.
For example, for those countries that have national proxies for Internet access (such as the United Arab Emirates for example), a terrorist could hack that proxy to: disrupt access, redirect to pornographic material, open up to all information, ...
Another example of terrorism could be the release of a virus/worm targetted at power plants. An example of vulnerability was given in this post:
Slammer worm and power plants
Aside from these electronic attacks, you could also imagine hitting physical infrastructure to disrupt global networks. For example, blowing up the Amsterdam Internet Exchange would have a severe impact on the Internet in the Netherlands and on trans-atlantic connections, since Amsterdam is one of the main European cities for connections to the US.
Back in May 2002, the International Telecommunication Union has a symposium on the security of information networks, trying to identify the weaknesses and the risks in a global network world. The US can strengthen its networks all it wants, but as long as these networks are then connected to other countries, you are creating weaknesses in your armour.
You can find more information on it at: Creating Trust In Critical Network Infrastructures
auio_head brings up an interesting point about the reach of the FBI in scanning Hotmail accounts. Since you are using a service provided by an American company located in the United States, this is understandable. However, did you know that the Patriot Act included a paragraph giving the United States the power to filter and scan every packet of information transiting through the United States. This means that for an email going from Europe to Australia, it would most likely transit through the US and suddenly fall under US jurisdiction.
The short of the story is that, as we get more reliant on communications networks, we also become more vulnerable to attacks against them. What was the impact on New York of a power outage? Tremendous. It even had an impact on trans-Atlantic Internet traffic and airlines in Europe. That's the result of our global environment.
Cheers,
BrainStop