The documents make clear that the CIA-operated drone campaign relies heavily on the NSA's ability to vacuum up enormous quantities of e-mail, phone calls and other fragments of signals intelligence, or SIGINT, the newspaper said.
The NSA created a secret unit known as the Counter-Terrorism Mission Aligned Cell, or CT MAC, to concentrate the agency's vast resources on hard-to-find terrorism targets, the Post reported.
The documents provided by Snowden don't explain how the bin Laden associate's email was obtained or whether it was obtained through the controversial NSA programs recently made public, including its metadata collection of numbers dialed by nearly every person in the United States.
Instead, the Post said its review of the documents indicates that the agency depends heavily on highly targeted network penetrations to gather information that wouldn't otherwise be trapped in surveillance nets that the NSA has set at key Internet gateways.
The U.S. has never publicly acknowledged killing bin Laden associate Hassan Ghul, according to the Post. The al-Qaida operative had been captured in 2004 and helped expose bin Laden's courier network, a key development in the effort to locate bin Laden. Ghul then spent two years in a secret CIA prison and returned to al-Qaida after the U.S. sent him to his native Pakistan in 2006.
U.S. forces killed bin Laden at his Pakistan hideout in 2011. That same year, the Treasury Department named Ghul a target of U.S. counterterrorism sanctions after he had helped al-Qaeda re-establish logistics networks, enabling al-Qaida to move people and money in and out of the country. The Post said an NSA document described Ghul as al-Qaida chief of military operations and detailed a broad surveillance effort to find him.
Obtained during a monthslong effort to find Ghul, the email from his wife erased doubts U.S. forces had found him, the Post said.