The centrifuges are hooked up to the internet? Sort of like leaving the chicken coop door open for the fox.
You're understanding of the situation is possibly wrong.
It is most likely that the Iranian nuclear facility is on a closed network. What has been speculated that the worm was downloaded onto the system via a portable flash drive plugged directly into one of the secured computer terminals in the system. Most likely a planted spy who works at the reactor.
I thought there are some Arab countries that are not infatuated with the prospect of Iran's ascension in that region. That being correct, it is sort of less than complimentary to Arabs to imply that only Israel may have the ability to play with such sophisticated computer viri. As usual, Israel (aka, Jews) makes for a convenient scape goat, regardless of who did it, in my opinion. Blaming a specific Arab country may be too politically inflammatory? Israel is used to being the racially profiled target.
I believe that in the world of developing countries, Israel might be seen as a proxy for European expansion in the Middle East. Sort of like a proxy left behind, after the colonial days. When is the world going to realize that Israel is not made up of a bunch of Jewish Europeans?