William Binney, creator of some of the computer code used by the National Security Agency to snoop on Internet traffic around the world, delivered an unusual message here in September to an audience worried that the spy agency knows too much.

It knows so much, he said, that it can’t understand what it has.

“What they are doing is making themselves dysfunctional by taking all this data,” Mr. Binney said at a privacy conference here.

The agency is drowning in useless data, which harms its ability to conduct legitimate surveillance, claims Mr. Binney, who rose to the civilian equivalent of a general during more than 30 years at the NSA before retiring in 2001. Analysts are swamped with so much information that they can’t do their jobs effectively, and the enormous stockpile is an irresistible temptation for misuse…

Messrs. Binney and Loomis also believed that ThinThread’s powers should be constrained to protect the privacy of Americans. Mr. Binney designed a way to encrypt all the U.S. metadata, and their plans allowed the spy agency’s analysts to unscramble the information only with permission from a warrant approved by the Foreign Intelligence Surveillance Court. The court oversees NSA activities that affect U.S. residents.