Released on Christmas Eve, the documents are heavily redacted versions of reports by the NSA to the President’s Intelligence Oversight Board

The National Security Agency used the holiday lull to “minimise the impact” of a tranche of documents by releasing them on Christmas Eve, the American Civil Liberties Union (ACLU) said on Friday.

The documents, which were released in response to a legal challenge by the ACLU under the Freedom of Information Act, are heavily – in some places totally –redacted versions of reports by the NSA to the President’s Intelligence Oversight Board dating back to 2007.

A court ordered the documents released this past summer, and a 22 December deadline for that release was agreed upon, according to Patrick Toomey, a staff attorney at the ACLU’s national security project, because the NSA said it needed “six or seven months” to complete its review and redaction process.

A spokesperson for the NSA said that the 22 December deadline, “which was agreed to by all parties,” was met.

But according to Toomey, the ACLU didn’t receive the documents until “late in the day on the 23rd” – the NSA sent them by FedEx late on the 22nd – and the NSA didn’t publicly release them until Christmas Eve. “I certainly think the NSA would prefer to have the documents released right ahead of the holidays in order to have less public attention on what they contain,” Toomey said.

The redactions on the document are extreme, and their omissions tantalising. One entry, from the 4th quarter of 2008, reads: “On [redacted] [redacted] used the US SIGINT System (USSS) to locate [redacted] believed to be kidnapped [redacted] The selectors were tasked before authorization was obtained from NSA. After the NSA Office of General Counsel (OGC) denied the authorization request, [redacted] was found. He had not been kidnapped.”

Another reads: “On [redacted] during an experimental collection and processing effort, NSA analysts collected [several lines of text redacted.] The messages were deleted [redacted] when the error was identified.”

Many entries are erased entirely, which means the documents reveal very little about how individuals who misuse the data were disciplined by the NSA, or how quickly errors were resolved.

But, according to Toomey, they speak to a total picture of a “large number of different compliance violations. We don’t know how many.”

He said the documents deepen the picture of the nature and extent of compliance violations by analysts working for the NSA.

“There are certain portions of the documents that really vindicate some of the things [Edward] Snowden said when he first described the NSA surveillance in terms of the ability of analysts to conduct queries – without authorisation – of raw internet traffic,” Toomey said.

Among the items redacted are sections detailing the total number of violations reported, with many ending up like this entry from 2013 “On [redacted] occasions during the fourth quarter, selectors were incorrectly tasked because of typographical errors.”

This makes the scale of the problem difficult to gauge. Toomey said the ACLU would continue to sue for the release of those numbers.

“More generally,” Toomey said, “just the range of different compliance violations makes it clear that at every step of the NSA’s collection of information there are vulnerabilities that leave the privacy of Americans at risk.”

A spokesperson for the NSA declined to answer the question of why Christmas Eve was chosen as a release date. A statement on the agency’s website which accompanied the documents’ release said: “These materials show, over a sustained period of time, the depth and rigor of NSA’s commitment to compliance.”

“By emphasizing accountability across all levels of the enterprise, and transparently reporting errors and violations to outside oversight authorities,” the statement concluded, “NSA protects privacy and civil liberties while safeguarding the nation and our allies.”