The UN nuclear agency has acknowledged that one of its computer servers was hacked by an anti-Israeli group.
The IAEA said a previously unknown group called Parastoo had posted contact details for more than 100 nuclear experts on the group’s website.
Parastoo asked those listed to sign a petition calling for an IAEA investigation into Israel’s undeclared nuclear weapons programme.
The IAEA is investigating Iran’s controversial nuclear programme.
Israel is widely believed to have nuclear weapons but neither confirms nor denies this under a “strategic ambiguity” policy.
International Atomic Energy Agency (IAEA) spokeswoman Gill Tudor said the agency “deeply regrets this publication of information stolen from an old server”.
She said the server had been shut down “some time ago” and experts had been trying to eliminate any “possible vulnerability” in it even before it was hacked.
“The IAEA’s technical and security teams are continuing to analyse the situation and do everything possible to help ensure that no further information is vulnerable,” she added.
The word Parastoo is Farsi for the bird species the swallow and an Iranian girl’s name.
The Vienna-based IAEA said the theft concerned “some contact details related to experts working” with the agency.
A Western diplomat quoted by Reuters news agency said the stolen data was not believed to include information related to confidential work carried out by the IAEA.
Israel, the US and other Western nations accuse Iran of secretly trying to develop nuclear weapons, a charge Tehran strongly denies.
Earlier this month, the IAEA said that Iran was ready to double the output at its underground uranium enrichment facility at Fordo.
In a report, it said it was unable to conclude that all nuclear material in Iran was for peaceful activities.
BBC
