The National Security Agency searched through its data troves of emails and other communications data for 198 "identifiers" of Americans' information in 2013 alone, a practice civil libertarians denounce as a way to evade constitutional privacy protections.



The figures were disclosed by the Office of the Director of National Intelligence following pressure from Senator Ron Wyden, the Oregon Democrat on the intelligence community who termed the data dives a "backdoor search."

They also showed that the Federal Bureau of Investigation and the Central Intelligence Agency also comb through NSA content databases – not simply data about communications – for Americans' information.



Exploiting leeway in rules to limit unreasonable data dissemination under a critical 2008 surveillance law, first revealed in August by the Guardian, the NSA relies on such content searches, which do not require judicial orders like subpoenas or warrants, to a previously unknown degree. The searches are conducted in secret, and they occur despite an assurance last year from President Obama that "nobody is listening to your telephone calls."

The 198 "identifiers" do not necessarily indicate 198 Americans had their information searched, nor do they necessarily indicate NSA performed 198 content searches for Americans during 2013. The NSA also conducted about 9,500 queries of associated "metadata" using US persons' identifiers – such as a phone number or email address - in 2013, and considers 36% of such queries "duplicative."

"The approved US person identifiers may have been used to conduct multiple queries, and NSA does not track the number of content queries made," Deirdre M Walsh, the legislative liaison for director of national intelligence James Clapper, told Wyden in a letter dated 27 June and released Monday.



During 2013, the CIA conducted "fewer than 1,900" communications queries using Americans' identifiers, with 27% of them being duplicative.



But Walsh not only confirmed that the FBI can perform the searches itself, she said the bureau does not tally how many communications searches for Americans' data it performs - and apparently mingles these international communications involving Americans with more traditional forms of legally acquired communications, confounding an accounting.

But the FBI, which can also search NSA's communications troves for "evidence of a crime" in addition to counterterrorism and espionage purposes, "believes the number of queries is substantial".



The disclosure of the "backdoor search" statistics comes as momentum builds in Congress and elsewhere for curbing the practice, bringing greater scrutiny to an aspect of NSA surveillance often overshadowed by the NSA's domestic call data dragnet.



An amendment banning the NSA from searching without warrants for Americans in its so-called "702" databases – so named for its legal authority, Section 702 of the 2008 Fisa Amendments Act – passed the House of Representatives last Thursday, by 293 votes to 121.



In the Senate, Wyden and others vow to place the ban on backdoor searches back into a surveillance bill supported by the White House and the NSA - a provision the Obama administration successfully removed from the House version that passed in May. The Senate judiciary committee is expected to take up the bill in the coming weeks.



"While intelligence officials have often argued that it is impossible to estimate how many Americans’ communications are getting swept up by the government under Section 702, the Fisa court has noted that the NSA acquires more than 250 million internet communications every year using Section 702, so even if US communications make up a small fraction of that total, the number of US communications being collected is potentially quite large," Wyden said in a statement on Monday.



Beyond the legislative pressure, the government's privacy watchdog, the Privacy and Civil Liberties Oversight Board, will deliver a major report on the "702" searches on Wednesday.



Yet months after the NSA abandoned its public defense of its bulk phone metadata collection, it forcefully defends its warrantless searches for Americans in its communications content troves.



During a public hearing about the ostensibly foreign-focused communications troves, senior intelligence and administration lawyers argued that wide discretion over combing through the databases is critical for detecting terrorism and espionage threats.

They further argued that as long as the secret surveillance court overseeing the data collection certifies that casting a vast surveillance net is legal, no warrant is required for searching through that net, even if Americans' data is contained within."Once you've lawfully collected that information, subsequently querying that information isn't a search under the fourth amendment, it's information already in the government's custody," Justice Department attorney Brad Weigmann contended in March.



About the only restriction on NSA's ability to query its communication troves is that such searches must be "reasonably likely to return foreign intelligence information," already a broad category, NSA chief lawyer Rajesh De told the panel in March.



From the perspective of privacy advocates, such searches route around intended privacy protections. Civil libertarians contend that legal restrictions preventing the government from intentionally targeting an American using surveillance tools for uncovering foreign intelligence information are nullified if the government can collect vast swaths of data and maintain unrestricted leeway to search through it.



"If there is evidence that a particular American is involved in terrorism or other nefarious activity, then intelligence and law enforcement agencies should absolutely investigate that person aggressively, by showing that evidence to a judge and getting a warrant. These searches are skirting the Constitution without making Americans any safer," Wyden stated after last week's House vote.



On Friday, the intelligence community released a highly anticipated transparency report – its first concerning NSA surveillance authorities – that said nearly 90,000 "targets" had their data reaped pursuant to a single Fisa court order under Section 702. That number surely undercounts the total figure of individuals surveilled, as a "target" can include an entire organization or even a foreign government.



But NSA did not disclose in the report how many Americans had their data accessed when caught in the ostensibly foreign-focused communications dragnets. Wyden extracted a promise to disclose the figure from NSA officials during a June 5 Senate intelligence committee hearing.



Wyden warned that the uncounted FBI searches posed a particular problem, both substantively and for oversight.



"When the FBI says it conducts a substantial number of searches and it has no idea of what the number is, it shows how flawed this system is and the consequences of inadequate oversight," Wyden said.



"This huge gap in oversight is a problem now, and will only grow as global communications systems become more interconnected. The findings transmitted to me raise questions about whether the FBI is exercising any internal controls over the use of backdoor searches including who and how many government employees can access the personal data of individual Americans. I intend to follow this up until it is fixed."

Walsh, in a seeming criticism of Wyden, disputed the "backdoor search" terminology and wrote, "contrary to some claims, there is no loophole in the law," nor any illegality around he searches.