The U.N.'s 18-acre plot on the East Side of Manhattan, punctuated by the 39-story-tall Secretariat building, is almost certainly the hub of the most spied-upon community in the world. Spokes of surveillance extend to the nearby brownstone buildings that house many of the missions of the U.N.'s 191 member countries -- and to the apartment buildings and restaurants where U.N. officials and workers live and dine.
At the U.N., the watchword is simple: Everybody spies on everybody else, friend and foe alike, all the time. Newcomers are advised to assume that their offices, homes, and cars are bugged. All phone calls and e-mails are intercepted, either with physical phone taps -- often several, installed by various countries -- or by the forest of antennas atop many buildings, which pluck electronic signals out of the air. The only countries that don't monitor others' electronic communications are those that can't afford to do so.
Then there's the U.S. National Security Agency's Echelon network, which can target e-mail and phone calls to and from the U.N., thanks to eavesdropping sites as far off as Britain or Australia. These sites have giant radio antennas that can pick up all traffic handled by communications satellites. Echelon's biggest listening post is at Menwith Hill in England's Yorkshire moors. It's run by Britain's counterpart of the NSA, the General Communications Headquarters (GCHQ).
Menwith Hill was the epicenter of a famous snooping fiasco that the NSA would no doubt like to sweep under the carpet. On Jan. 31, 2003, the NSA sent a top-secret e-mail asking GCHQ translators to pay particular attention to phone calls and electronic messages to and from the six temporary members of the U.N. Security Council. Washington wanted to know the "whole gamut of information that could give U.S. policymakers an edge" in the arm-wrestling over U.N. deliberations to authorize the invasion of Iraq. Katharine Gun, a 29-year-old translator at Menwith Hill, was outraged. She leaked the message to the press.
Early last year, London elected not to prosecute Gun. Clare Short, who had spent six years as international development secretary in Prime Minister Tony Blair's cabinet, was interviewed on radio about the decision. During the broadcast, Short dropped a bombshell: "The UK in this time  was also spying on Kofi Annan's office," she said. "I have seen transcripts of Kofi Annan's conversations."
READ THEIR LIPS.
Back at the U.N., Short's revelation caused barely a ripple. Eavesdropping is so endemic that some countries, such as Pakistan and Bulgaria, rarely bother to summon technicians to sweep their offices with bug-detecting equipment. Any bug removed today will just get replaced tomorrow, they figure. Besides, the eavesdropping device might be across the street or in a parked car -- for example, lasers trained on windows can record minute vibrations in the glass created by conversations and translate those movements back into sounds.
In movies, surveillance subjects often stroll in the park (the U.N. has a small one) to escape listening devices. But that's no guarantee of privacy, either. There are long-range sound microphones that can zoom in on a particular person from a distance. Or a lip-reading spook may be following an outdoor conversation through binoculars.
Lip readers often vie for strategic tables at restaurants so they can monitor the lunch talk of U.N. officials. The U.N. folks know this, and they've become experts at whispering through clenched teeth or behind menus when they say anything confidential.
SPY IN THE POCKET.
So where do U.N. diplomats go to hold secret talks? The missions of many countries have specially constructed, windowless and soundproof rooms. Often, they also boast electronic shields, typically a wire mesh, under all surfaces -- walls, floor, and ceiling. Those rooms get a once-over with bug-detecting gear before each session.
For added security, participants are usually asked either to leave their cell phones outside or to turn them off. That's because a cell phone can be used as a bug. In addition to the frequency over which users normally chat, cell phones have another frequency for communicating with a base station.
Intelligence agencies can use this control frequency to open the microphone of a turned-on, idle cell phone and -- unbeknownst to the user -- eavesdrop on whatever is transpiring in the vicinity. The same goes for the cellular-radio systems in cars, such as General Motors's (GM ) OnStar technology.
Digital cell phones that use frequency hopping, known as spread-spectrum technology, are safe from most commercial scanners. But not from some spy agencies, which use equipment that pretends to be a base station and disables the handset's frequency hopping. Or they can pull a cloak-and-dagger job and install taps at a cellular company's base station.
INCESSANT AND INEVITABLE.
What's it like to live under constant and continual surveillance? U.N. staffers shrug and say, "You get used to it." Of course, their own country's spies are probably playing the game, too, so they can't complain too much.
Maybe that's how all the worrying and gnashing of teeth over the erosion of privacy in this post-9/11 world will culminate: in resignation.
If snooping technology becomes so common that almost anyone can stick a nose into the affairs of anyone else, as seems likely, everyone will just take it for granted. The U.N. may be a preview of what's in store for all of us.
By BusinessWeek Senior Writer Otis Port in New York