just semantics
If the line between cyber crime and cyber warfare is thin, the line between cyber terrorism and cyber warfare is even thinner. At exactly what point does an act of terror become an act of war? There have been governments who have engaged in terrorist activities, and non-government groups who have started wars, most times by overthrowing an existing government, and then going from there. And governments can get away with more questionable and borderline activities, since about the only way to prosecute another government is to go to war, and nobody's going to declare war based on questionable or borderline activities.
And it's doubtful there will be much proof of planning for a cyber terror attack. Anything that does show up on the radar would often be called an accident, like the one you mentioned, or maybe even a demonstration to show that such an attack is possible, and then they (assuming they're not already a known terrorist group) could claim that they are working on ways to prevent such an attack from being made by a terrorist. Of course, if something shows up and they ARE a known terrorist group, well then they just unzipped their fly, showed their hand, or any other way you want to say their ball game is over.
It could also become the onset of a cyber cold-war. Except back in the cold war, detecting an enemy attack could give the opposing side enough time to launch a counter-attack, which is why it stayed a cold war. In a cyber-offensive, it takes seconds for the attack to reach its destination, instead of hours, and a well-placed cyber-offensive could prevent a counter-offensive altogether. A little unnerving when you think of it that way.
