Top experts kept a close eye on a major global cyber attack that swept the world, as they gathered on Wednesday in Tel Aviv for an annual cyber security conference.The attack disrupted computers at Russia's biggest oil company, Ukrainian banks and multinational firms with a virus similar to the ransomware that infected more than 300,000 computers last month.The rapidly spreading cyber extortion campaign, which began on Tuesday, underscored growing concerns that businesses have failed to secure their networks from increasingly aggressive hackers, who have shown they are capable of shutting down critical infrastructure and crippling corporate and government networks.Businesses in the Asia-Pacific region reported some disruptions on Wednesday with the operations of several European companies hit, including India's largest container port, although the impact on companies and governments across the wider region appeared to be limited.Professor Isaac Ben Israel, head of the Blavatnik Cyber Research Center at Tel Aviv university, said, "If you ask what is my speculation about it, I would guess that the main attack here was an attack on Ukraine and it was masked by the ransomware attack that happened, as I said, in many other countries. And if you ask me, again, the attack we had a few weeks ago, the 'WannaCry', was only one stage to lead us towards the suspicion in other entities, and not the natural suspicion in case of attacking Ukraine, which is Russia."On the other hand, Michael Daniel, president of the Cyber Threat Alliance and form cyber security coordinator at the White House, said, "We'll have to see where the evidence leads in this particular case. I mean, Ukraine, you know, Russia is the obvious target for Ukraine to point at but there are many many criminal organizations in the world based in many different countries. And it could be a criminal organization, it could be a hacktivist, it could be a nation state, so it's just really too soon to tell."