As immense as the NSA's mission has become -- patrolling the world's data fields in search of terrorists, spies, and computer hackers -- it is merely one phase of Alexander's plan. The NSA's primary mission is to protect government systems and information. But under his leadership, the agency is also extending its reach into the private sector in unprecedented ways.
Toward the end of George W. Bush's administration, Alexander helped persuade Defense Department officials to set up a computer network defense project to prevent foreign intelligence agencies --mainly China's -- from stealing weapons plans and other national secrets from government contractors' computers.
Under the Defense Industrial Base initiative, also known as the DIB, the NSA provides the companies with intelligence about the cyberthreats it's tracking. In return, the companies report back about what they see on their networks and share intelligence with each other.
Pentagon officials say the program has helped stop some cyber-espionage. But many corporate participants say Alexander's primary motive has not been to share what the NSA knows about hackers. It's to get intelligence from the companies -- to make them the NSA's digital scouts. What is billed as an information-sharing arrangement has sometimes seemed more like a one-way street, leading straight to the NSA's headquarters at Fort Meade.
"We wanted companies to be able to share information with each other," says the former administration official, "to create a picture about the threats against them. The NSA wanted the picture."
After the DIB was up and running, Alexander proposed going further. "He wanted to create a wall around other sensitive institutions in America, to include financial institutions, and to install equipment to monitor their networks," says the former administration official. "He wanted this to be running in every Wall Street bank."
That aspect of the plan has never been fully implemented, largely due to legal concerns. If a company allowed the government to install monitoring equipment on its systems, a court could decide that the company was acting as an agent of the government. And if surveillance were conducted without a warrant or legitimate connection to an investigation, the company could be accused of violating the Fourth Amendment. Warrantless surveillance can be unconstitutional regardless of whether the NSA or Google or Goldman Sachs is doing it.
"That's a subtle point, and that subtlety was often lost on NSA," says the former administration official. "Alexander has ignored that Fourth Amendment concern."
The DIB experiment was a first step toward Alexander's taking more control over the country's cyberdefenses, and it was illustrative of his assertive approach to the problem. "He was always challenging us on the defensive side to be more aware and to try and find and counter the threat," says Tony Sager, who was the chief operating officer for the NSA's Information Assurance Directorate, which protects classified government information and computers. "He wanted to know, 'Who are the bad guys? How do we go after them?'"
While it's a given that the NSA cannot monitor the entire Internet on its own and that it needs intelligence from companies, Alexander has questioned whether companies have the capacity to protect themselves. "What we see is an increasing level of activity on the networks," he said recently at a security conference in Canada. "I am concerned that this is going to break a threshold where the private sector can no longer handle it and the government is going to have to step in."