By Max McCoy

Globe Investigative Writer

JANE, Mo. - Call it Area 71.

Behind a fence topped with razor wire just off U.S. Highway 71 is a bunker of a building that Wal-Mart considers so secret that it won't even let the county assessor inside without a nondisclosure agreement.

The 125,000-square-foot building, tucked behind a new Wal-Mart Supercenter, is only a stone's throw from the Arkansas line and about 15 miles from corporate headquarters in Bentonville, Ark.

There is nothing about the building to give even a hint that Wal-Mart owns it.

Despite the glimpses through the fence of manicured grass and carefully placed trees, the overall impression is that this is a secure site that could withstand just about anything. Earth is packed against the sides. The green roof - meant, perhaps, to blend into the surrounding Ozarks hills - bristles with dish antennas. On one of the heavy steel gates at the guardhouse is a notice that visitors must use the intercom for assistance.

What the building houses is a mystery.

Speculation

Wal-Mart's ability to crunch numbers is a favorite of conspiracy theorists, and its data centers are the corporate counterpart to Area 51 at Groom Lake in the state of Nevada. According to one consumer activist, Katherine Albrecht, even the wildest conspiracy buff might be surprised at just how much Wal-Mart knows about its customers - and how much more it would like to know.

"We were contacted about two years ago by somebody who runs a security company that had been asked in a request for proposals for ways they could link video footage with customers paying for their purchases," Albrecht said. "Wal-Mart would actually be able to view photos and video of customers paying, say, for a pack of gum. At the time, it struck me as unbelievably outlandish because of the amount of data storage required."

But Wal-Mart, according to a 2004 New York Times article, had enough storage capacity to contain twice the amount of all the information available on the Internet. For the technically minded, the exact amount was for 460 terabytes of data. The prefix tera comes from the Greek word for monster, and a terabyte is a trillion bytes, the basic unit of computer storage.

Albrecht, founder of Consumers Against Supermarket Privacy Invasion and Numbering, said she never could confirm the contractor's story. That is not surprising, since Wal-Mart seldom comments on its data capabilities and operations.

A Globe request for information about the Jane data center was referred at Wal-Mart headquarters to Carrie Thum, a senior information officer and former lobbyist for the retailer.

"This is not something that we discuss publicly," Thum said. "We have no comment. And that's off the record."