The recent revelation that the Israelis had obtained classified information relating to the P5+1 negotiations with Iran over the latters nuclear program should not really surprise anyone. Israel has invested a great deal of political capital in confronting Iran and convincing the American public that it poses a genuine threat. So, it would be a given that its intelligence service, Mossad, would be tasked with finding out what information is not being shared by the White House.
But the truly intriguing back-story to this development is, how did the Israelis do it and with whom exactly did they share their information? The information obtained was described by the White House as eavesdropping, which would suggest some sort of electronic interception. But as the meetings undoubtedly took place in a technically secured room, which means that it was electronically swept before, during, and after meetings, the conversations could not be picked up either from bugs planted inside which would be detected or from penetration techniques originating outside, which is possible but would require a major deployment of high-tech gear close to the target.
Eliminating a sigint source suggests that the intelligence was either obtained from careless conversations on unsecured phones (possible but unlikely given the tightened security in response to recent flaps over such use), or through a spy in the room feeding the information to the Israelis. A spy is, regrettably, more likely and one has to wonder if the leaker was/is part of the American delegation because the information appears to be of such a nature as to come from US sources. This would mean that the American negotiating team has been penetrated by the Israelis.
And the other issue is, of course, the question of who in Congress received the stolen information during the regular briefings that Israeli embassy staff, including intelligence officers, give to legislators on Capitol Hill. Did they know or suspect that what they were being told was obtained through Israeli espionage? Did it occur to them that the Israeli narrative on what was taking place differed in detail from what they were hearing from the White House, suggesting that something was afoot? Deference to Israeli interests is normal in many in Congress, perhaps all too normal, but a lack of awareness of the American interests at stake in the game constitutes malfeasance at a much higher level.