The Wall Street Journal reports: The classified information that President Donald Trump shared with Russian officials last week came from an Israeli source described by multiple U.S. officials as the most valuable source of information on external plotting by Islamic State.

These officials, who are privy to intelligence about the terrorist group’s efforts, said the source of information was particularly valuable for tracking Islamic State’s attempts to place explosive devices on commercial airplanes.

However, the officials disagree over how much damage Mr. Trump may have caused to counterterrorism efforts by discussing information gleaned from Israel with the Russians during an Oval Office meeting last week.

One official said now that the Russians are aware of the source, there is greater risk the source could be compromised in some way. That makes it less likely that the intelligence community will trust future information, the official said.

But another official doubted that the Russians would be able to identify the nature of the source based on Mr. Trump’s statements, though Moscow might learn more about where in Syria the intelligence was coming from.

While not the only source of information on the threat to airlines, it was considered the most important, the officials said. Based on cumulative intelligence, the U.S. has barred carry-on laptop computers and other consumer electronic equipment from 10 airports in the Middle East and is considering expanding the ban.

To avoid further damage, the U.S. officials declined to specify whether the source of information is an individual or part of a technological system. But their unanimous agreement on the importance of the source to one of Washington’s top national security objectives—countering international plots by Islamic State—underscores the gravity of the Oval Office conversation and the potential repercussions for Mr. Trump of sharing information that was supposed to be restricted to the U.S. and Israel. [Continue reading…]