According to a report published in the New York Times, British, Indian, and American intelligence agencies failed to piece together major plot details of Pakistani terrorist group Lashkar-e-Taiba before they carried out the gruesome, three-day onslaught in Mumbai in 2008 that left 166 dead, including six Americans.

The report published in today's Times was assembled with ProPublica, the PBS series Frontline, and classified documents leaked by Edward Snowden, the former NSA contractor. Their investigation reveals that the online activity of Zarrar Shah—the technology chief of Lashkar-e-Taiba who used Google Earth to help map routes to the group's targets in Mumbai—was being monitored by international intelligence groups ahead of the attacks. From the Times:

But he did not know that by September [2008], the British were spying on many of his online activities, tracking his Internet searches and messages, according to former American and Indian officials and classified documents disclosed by Edward J. Snowden, the former National Security Agency contractor.

They were not the only spies watching. Mr. Shah drew similar scrutiny from an Indian intelligence agency, according to a former official briefed on the operation. The United States was unaware of the two agencies' efforts, American officials say, but had picked up signs of a plot through other electronic and human sources, and warned Indian security officials several times in the months before the attack.

When the militants began their attack on Nov. 26, American agencies scrambled to make sense of the major clues collected ahead of time:

The killing was indiscriminate, merciless, and seemingly unstoppable over three horrific days. In raw, contemporaneous notes by analysts, the eavesdroppers seem to be making a hasty effort to understand the clues from the days and weeks before.

"Analysis of Zarrar Shah's viewing habits" and other data "yielded several locations in Mumbai well before the attacks occurred and showed operations planning for initial entry points into the Taj Hotel," the N.S.A. document said.

Indeed, key details of the group's attacked appear to have been previously gathered by British, American, or Indian intelligence agencies but went either unshared with their international counterparts, were passed over in the large passels of data, or just ignored:

The British had access to a trove of data from Mr. Shah's communications, but contend that the information was not specific enough to detect the threat. The Indians did not home in on the plot even with the alerts from the United States.

For example, the British apparently learned early on that Shah was working to access a New Jersey-based voice-over-Internet phone service (VoIP) to mask calls from Pakistan to Lashkar-e-Taiba agents in Mumbai:

Mr. Shah had begun researching the VoIP systems, online security, and ways to hide his communications as early as mid-September, according to the documents. As he made his plan, he searched on his laptop for weak communication security in Europe, spent time on a site designed to conceal browsing history, and searched Google News for "indian american naval exercises" — presumably so the seagoing attackers would not blunder into an overwhelming force.

"If Mr. Shah made any attempt to hide his malevolent intentions, he did not have much success at it," the Times writes. "Although his frenetic computer activity was often sprawling, he repeatedly displayed some key interests: small-scale warfare, secret communications, tourist and military locations in India, extremist ideology and Mumbai":

He searched for Sun Tzu's "Art of War," previous terror strikes in India and weather forecasts in the Arabian Sea, typed "4 star hotel in delhi" and "taj hotel," and visited mapsofindia.com to pore over sites in and around Mumbai, the documents show.

Still, the sheer scale of his ambition might have served as a smokescreen for his focus on the city. For example, he also showed interest in Kashmir, the Indian Punjab, New Delhi, Afghanistan and the United States Army in Germany and Canada. He constantly flipped back and forth among Internet porn and entertainment sites while he was carrying out his work. He appeared to be fascinated with the actor Robert De Niro, called up at least one article on the singer Taylor Swift, and looked at funny cat videos. He visited unexplainable.net, a conspiracy theory website, and conducted a search on "barak obama family + muslim."

"His fascination with jihad," the Times goes on, "established him as something of a pioneer for a generation of Islamic extremists who use the Internet as a weapon."

Intelligence had apparently also been collected on David Coleman Headley, the Pakistani-American co-conspirator in the plot that was arrested by officials months after the attack:

Clues slipped by the Americans as well. David Coleman Headley, a Pakistani-American who scouted targets in Mumbai, exchanged incriminating emails with plotters that went unnoticed until shortly before his arrest in Chicago in late 2009. United States counterterrorism agencies did not pursue reports from his unhappy wife, who told American officials long before the killings began that he was a Pakistani terrorist conducting mysterious missions in Mumbai.

Britain's Government Communications Headquarters denied that the intelligence gathered warranted raised suspicions. A spokesman told the Times, “We do not comment on intelligence matters. But if we had had critical information about an imminent act of terrorism in a situation like this we would have shared it with the Indian government. So the central allegation of this story is completely untrue.”

And U.S. Brian Hale, a spokesman for the director of the Office of National Intelligence, told the Times, "While I cannot comment on the authenticity of any alleged classified documents, N.S.A. had no knowledge of any access to a lead plotter's computer before the attacks in Mumbai in November 2008."

"No one put together the whole picture," Shivshankar Menon, who was India's foreign minister at the time of the attacks, told the Times. "Not the Americans, not the Brits, not the Indians."

[Image via AP]