US and Israel were behind Stuxnet claims researcher (opens in new tab)

I disagree. That question is all but meaningless. I see no evidence that any portion of the international community gives a rat's ass about "acts of war". Many people try to cover this up by pointing fingers at some chosen target and showing about how they flout the old European rules for how countries should relate to each other, but since nobody follows them finding some entity that did would just prove that entity to be a chump. It does make it easy to point fingers and try to distract you with a song and dance about how evil some individual party is, since everyone has a list of violations of the old European laws/concepts a mile long now. Some parts of the international community like to talk about it when it is convenient but disappear instantly when it becomes the slightest bit inconvenient.

("So you're saying the actions of $SOME_DISFAVORED_ENTITY are just OK with you, then?" No, I'm saying the dimensions I measure ethical behavior on have little to do with the phantom international law system. It only works when most or all participants agree to be bound by it, something that has not been true within my lifetime. I have not given you enough info in this post to guess what my judgments are.)

I've heard the issue discussed by interested parties, though certainly not international law scholars. It seems the commonly held opinion is also a rather simple one - an electronic attack that causes a building to explode would be the same as bombing the building, stealing classified documents electronically is espionage, and so fouling nuclear enrichment would be sabotage.

The critical difference is proving who did it. If you want to prove who bombed your building often there is some physical evidence that can be pretty conclusive. Chemical signatures of the explosives, photographs from customs, caught on video, what type of plane it was etc.

Electronic attacks often fall more in the lines of having circumstantial evidence. Even if "everyone knows" who did it, it probably falls short of proof unless someone takes credit.

Is sabotage an act of war? I'm not sure if there is a set standard. In practice it often seems to get a pass - the CIA was apparently responsible for sabotaging a pipeline in Siberia in 1982 without any international outcry. Especially in the realm of non-proliferation the international community seems to be mostly united. Even overt action like the Israeli bombing of Syrian nuclear sites in 2007 received a muted response at best.

Are the United States and Iran already at war? Iran held US displomats hostage.

Are Israel and Iran at war? The president of Iran called for the destruction of Israel. Does the count as a declaration of war?

What is a legal vs. illegal attack? Is there an authority that determines legality in this case? If it rules the attack is illegal, how is the attack prevented of the perpetrator punished? If we have all that what's up with Gaddafi or Myanamar or North Korea etc etc?

Do you think there were reasons behind such an infection coming from Iran? Were they an act of war?

If both were true, then USA is in trouble for Iraq for much more than creating a computer virus with intent.

There's also http://www.net-security.org/secworld.php?id=10596 where an Israeli general supposedly is given credit for the attack which make it sound like it's a pretty "open secret"