WASHINGTON — As the nation's spy agencies assess the fallout from disclosures about their surveillance programs, some government analysts and senior officials have made a startling finding: The impact of a leaked terrorist plot by al-Qaida in August has caused more immediate damage to U.S. counterterrorism efforts than the thousands of classified documents disclosed by Edward Snowden, the former National Security Agency contractor, the New York Times reported Sunday, citing unnamed officials.
Since news reports in early August revealed that the United States intercepted messages between Ayman al-Zawahri, who succeeded Osama bin Laden as the head of al-Qaida, and Nasser al-Wahishi, the head of the Yemen-based al-Qaida in the Arabian Peninsula, discussing an imminent terrorist attack, analysts have detected a sharp drop in the terrorists' use of a major communications channel that authorities were monitoring.
Since August, senior U.S. officials have been scrambling to find new ways to tap into the electronic messages and conversations of al-Qaida's leaders and operatives.
The switches weren't turned off but there has been a real decrease in quality of communications, said one U.S. official, who like others spoke to the New York Times on the condition of anonymity to discuss intelligence.
The drop in message traffic after the communication intercepts contrasts with what analysts describe as a far more muted impact on counterterrorism efforts from the disclosures by Snowden of the broad capabilities of NSA surveillance programs. Instead of terrorists moving away from electronic communications after those disclosures, analysts have detected terrorists mainly talking about the information that Snowden has disclosed.
Senior U.S. officials say that Snowden's disclosures have had a broader impact on national security in general. This includes fears that Russia and China now have more technical details about the NSA surveillance programs.
The communication intercepts between al-Zawahri and al-Wahishi revealed what U.S. intelligence officials and lawmakers have described as one of the most serious plots against U.S. and Western interests since the attacks on Sept. 11, 2001. It prompted the closure of 19 U.S. Embassies and consulates for a week, when the authorities concluded the plot focused on the embassy in Yemen.
U.S. officials say they believe the disclosure about the plot has had a significant impact because it signaled to terrorists that a main communication network that the group's leaders were using was being monitored.