Originally published January 15, 2015 at 9:40 AM | Page modified January 15, 2015 at 12:26 PM

A committee of scientific experts has concluded that there is no viable technological alternative to bulk collection of data by the National Security Agency that allows analysts access to communications whose significance only becomes clear years later.

An 85-page report by the National Research Council, commissioned last year in the wake of surveillance revelations by former NSA contractor Edward Snowden, did not take a position on the merits of bulk collection of telephone or other records. But asked to look for effective software alternatives to bulk collection, it concluded there weren't any, in cases when, for example, the NSA wants to examine the past communications of new terror suspects.

"Restricting bulk collection will make intelligence less effective, and technology cannot do anything about this," the report says. 'Whether the gain in privacy is worth the loss is a policy question that the committee does not address."

If a particular set of communications becomes significant, the report says, "because of new circumstances such as identifying a new target, a non-nuclear nation that is now pursuing the development of nuclear weapons, an individual that is found to be a terrorist, or new intelligence-gathering priorities_historical events and the data they provide will be available for analysis only if they were previously collected."

The report does suggest ways to mitigate the privacy impact of bulk collection by restricting use of the data, something NSA says it does.

"Although no software can fully replace bulk with targeted information collection, software can be developed to more effectively target collection and to control the usage of collected data," the report says.

It recommends the use of automatic controls on bulk data, with audits that can be publicly shared.

The study was conducted by a committee of the National Academies, which advises the government on scientific matters. The committee was chaired by Robert Sproull, a former Oracle executive and computer scientist now at the University of Massachussetts.

The committee included a variety of experts, including Michael Leiter, former director of the National Counter Terrorism Center.

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Science panel: No alternative to NSA bulk data collection