The National Security Agency (NSA) released hundreds of pages of reports previously classified as 'top secret' on Christmas Eve.

They show dozens of instances in the last decade where the NSA spied on U.S. citizens.

The documents were released in response to a legal challenge by the American Civil Liberties Union under the Freedom of Information Act. The files -- a collection of quarterly and annual reports sent from the NSA's inspector general to the president's Intelligence Oversight Board dating back to 2001 -- are heavily redacted.

Among the reports are examples of data on Americans being e-mailed to unauthorized recipients, stored in unsecured computers and retained after it was supposed to be destroyed.

"There are certain portions of 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 authorization -- of raw internet traffic," Patrick Toomey, staff attorney, ACLU's national security project, told Bloomberg

Congress considered new legislation this year, the USA Freedom Act, which would have ended the NSA's domestic call tracking program, but it died in the Senate earlier in the year despite support from the ACLU and the National Rifle Association.

One document, a quarterly report compiled for the president's Intelligence Oversight Board in early 2012, reveals that an NSA agent even routinely spied on her spouse for upwards of three years. Such cases apparently occurred enough to have earned the name LOVEINT.

"In an interview," the report reads in part, "... the analyst reported that, during the past two or three years, she had searched her spouse's personal telephone directory without his knowledge to obtain names and telephone numbers for targeting."

"Although the investigation is ongoing, the analyst has been advised to cease her activities," the report continues.

Among the items redacted are sections showing the number of violations reported.

The reports show "how the NSA has misused the information it collects [sic] over the past decade," Toomey told the Wall Street Journal, and "... shows an urgent need for greater oversight by all three branches of government."