How big is big brother?

• Author: Magnuson, Stew
• Position: SECURITY BEAT: Homeland Defense Briefs

AS THE NATION DEBATES how far the National Security Agency can or should go in the realm of domestic eavesdropping, two noted professors have cautioned against giving the secretive organization too much credit.

Steven Bellovin, a computer science professor at Columbia University, says it is simply beyond the NSA's ability to monitor every phone call and every Web download.

"You cannot possibly collect everything," he told a gathering of military writers.

One Internet service provider, for example, has several nodes, each with the ability to handle 10 gigabits per second. The highest commercial off the shelf storage disks in the market can hold 300 gigabits. One disk would be filled within 15 minutes, he claimed.

"Even NSA can't collect that much data," he said. "Even if there was

one spot where you could collect it all, they can't possibly store it." It would be prohibitively expensive even by government standards; in the hundreds of billions of dollars, he added.

It's important to understand the difference between law enforcement surveillance versus intelligence surveillance, he said. Law enforcement is usually looking at individuals and involves court-issued warrants. Intelligence surveillance is more akin to a security sweep. They are looking for patterns.

"The best intelligence in the world can never give you proof beyond a reasonable doubt," he said. Signals can be faked, and modern encryption codes are difficult and expensive to crack...