And two senators who have consistently raised red flags about possible privacy violations stemming from NSA programs indicated there is more to be revealed.
"We believe Americans should know that this confirmation is just the tip of a larger iceberg," said Democratic Sens. Mark Udall of Colorado and Ron Wyden of Oregon in a statement. Both declined to provide details, citing Senate rules about discussing classified information.
Proposed legislation to dismantle the programs was narrowly defeated last month in the House. The July legislative effort brought together Libertarian-leaning conservatives and liberal Democrats who pressed for change against congressional leaders and lawmakers focused on security.
A week ago, Obama sought to soothe concerns by promising to consider reforms to NSA surveillance.
"It's not enough for me to have confidence in these programs," he said at a White House news conference. "The American people have to have confidence in them as well."
He announced changes such as convening an outside advisory panel to review U.S. surveillance powers, although it is unclear how that would differ from the existing U.S. Privacy and Civil Liberties Oversight Board, mandated by Congress to monitor surveillance and constitutional concerns. Obama also said the NSA would hire a privacy officer -- though the NSA already has a compliance office. None of those measures would seem likely to stop the kind of inadvertent collection of information that was described in the NSA audit.
In the typographical error category, the Post cited a 2008 example of the collection of a "large number" of phone records from Washington, D.C., when a programming error confused the District of Columbia area code 202 for 20-2, the international dialing code for Cairo, according to a quality assurance review that was not distributed to the NSA's oversight staff.
The NSA also saw a spike in the number of "roamers," or overseas, phone calls wrongly tracked in the first quarter of 2012, when those roamers traveled into U.S. territory, which is outside NSA's authority. The report said the errors may have been due to tracking Chinese who were visiting friends and relatives for the Chinese lunar new year.
In another case, the Foreign Intelligence Surveillance Court, which has authority over some NSA operations, did not learn about a new collection method until it had been in operation for many months. The court ruled it unconstitutional.
The FISC's chief judge told the Post that the court could rule only on the material it was given.
"The FISC is forced to rely upon the accuracy of the information that is provided to the Court," U.S. District Judge Reggie Walton said in a written statement to the Post. "The FISC does not have the capacity to investigate issues of noncompliance, and in that respect the FISC is in the same position as any other court when it comes to enforcing [government] compliance with its orders."
The Associated Press made a request to Walton for that statement. A court official said the judge had no response.
The White House declined Friday to comment on the latest revelations. It directed questions to the National Security Council, and NSC spokeswoman Caitlin Hayden directed questions to the NSA.
NSA spokeswoman Vanee Vines said the number of incidents in the first quarter of 2012 was higher than normal, and that the number has ranged from 372 to 1,162 in the past three years, due to factors such as "implementation of new procedures or guidance with respect to our authorities that prompt a spike that requires `fine tuning,' changes to the technology or software in the targeted environment for which we had no prior knowledge, unforeseen shortcomings in our systems, new or expanded access, and `roaming' by foreign targets into the U.S., some of which NSA cannot anticipate in advance but each instance of which is reported as an incident."
"When NSA makes a mistake in carrying out its foreign intelligence mission, the agency reports the issue internally and to federal overseers -- and aggressively gets to the bottom of it," Vines said.
When asked why the Post did not publish the story earlier, though the paper said it had the documents for months, spokeswoman Kris Coratti emailed Friday that "it has taken some time to study them and understand the information they contain."
The AP filed a Freedom of Information Act request to the NSA on June 17 asking for all copies of "minimization procedures" the agency uses to avoid collecting Internet and telephone data from U.S. citizens. That request sought documents that would also detail how the government purges records that may have been accidentally collected. The AP has yet to receive responsive material, though the NSA agreed to fast-track its request.