Data Intercept Technology Unit (DITU) is the NSA's indispensable partner in its global spying operations: an obscure, clandestine unit of the FBI

When the media and members of Congress say the NSA spies on Americans, what they really mean is that the FBI helps the NSA do it, providing a technical and legal infrastructure that permits the NSA, which by law collects foreign intelligence, to operate on U.S. soil. It's the FBI, a domestic U.S. law enforcement agency, that collects digital information from at least nine American technology companies as part of the NSA's Prism system. It was the FBI that petitioned the Foreign Intelligence Surveillance Court to order Verizon Business Network Services, one of the United States' biggest telecom carriers for corporations, to hand over the call records of millions of its customers to the NSA.

But the FBI is no mere errand boy for the United States' biggest intelligence agency. It carries out its own signals intelligence operations and is trying to collect huge amounts of email and Internet data from U.S. companies -- an operation that the NSA once conducted, was reprimanded for, and says it abandoned.

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