Every day, every minute, video cameras scan the crowds in a busy shopping center. But this is no ordinary public surveillance system. The faces of all those passersby are being converted into digital code and processed by computer. Continuously, instantaneously, the facial code of each stranger is compared with that of several dozen local criminals. If there is a match, an alarm sounds in a control room, a human operator double-checks the computer's assessment and alerts the police. Someone they want to keep tabs on, or someone they want to arrest, is in town …

This is not a scene from some Orwellian future. The system has been running for a year on the streets of Newham in East London--the first trial of its kind in the world. And the potential for this kind of system doesn't stop there. You would also expect this technology to be leapt on by state security services, such as those unseen watchers who scan airport crowds for terrorists and drug smugglers. And sure enough, a face-recognition system devised by Neurodynamics, a company based in Cambridge, England, is being tested in secret at a British airport.

Facial recognition technology creates new opportunities for companies and government agencies that want to keep tabs on people. We are our faces. To our fellow human beings, they are the key identifiers. Our brains have exquisite machinery for processing and storing a particular arrangement of eyes, nose and mouth and for picking it out from other very similar arrangements. This ability is now being passed on to computers.

They can spot people who are on the move and are not facing square on to the camera, and they can compensate for changing light levels. Visionics of New Jersey, the company behind the trials in Newham, claims that its technology is not even fooled by hats, spectacles, beards and moustaches.

Surveillance is not the only way this technology can be used. But what is so special, and slightly sinister about facial recognition technology, is that people need never know that their identity is being checked, which is where many surveillance projects begin.

If Newham's trial is eventually pronounced a success in reducing crime, then it may well be extended to other public surveillance systems, first in Britain and then elsewhere. And if these systems share a large, common database then criminals on it would, in effect, be "electronically tagged." The police would know whenever they showed their faces in any place covered by cameras.

Clearly this could be a powerful deterrent to crime, but it would take us a big step nearer to a world in which Big Brother really is continuously watching everyone.

So the spread of this technology raises an old but important question: who guards the guardians? How serious a crime do you have to commit before your face goes on a system? How long do you have to stay clear of crime before your face is removed? Do you have the right to know that you are on a database?

The Clinton administration reportedly plans to ask Congress to give police authority to secretly go into people's personal computers and crack their security codes.

Legislation drafted by the Justice Department would let investigators get a sealed warrant from a judge to enter private property, search through computers for passwords and override encryption programs, The Washington Post reported.

The newspaper quoted an Aug. 4 department memo that said encryption software for scrambling computer files "is increasingly used as a means to facilitate criminal activity."

Imagine a global spying network that can eavesdrop on every single phone call, fax or e-mail, anywhere on the planet. It sounds like science fiction, but it's true.

Two of the chief protagonists - Britain and America - officially deny its existence. But the BBC has confirmation from the Australian Government that such a network really does exist and politicians on both sides of the Atlantic are calling for an inquiry.

On the North Yorkshire moors above Harrogate they can be seen for miles, but still they are shrouded in secrecy. Around 30 giant golf balls, known as radomes, rise from the US military base at Menwith Hill.

Linked to the NSA

Inside is the world's most sophisticated eavesdropping technology, capable of listening-in to satellites high above the earth.

Facility is said to be capable of 2m intercepts per hour

The base is linked directly to the headquarters of the US National Security Agency (NSA) at Fort Mead in Maryland, and it is also linked to a series of other listening posts scattered across the world, like Britain's own GCHQ.

The power of the network, codenamed Echelon, is astounding.

Every international telephone call, fax, e-mail, or radio transmission can be listened to by powerful computers capable of voice recognition. They home in on a long list of key words, or patterns of messages. They are looking for evidence of international crime, like terrorism.

Open Oz

The network is so secret that the British and American Governments refuse to admit that Echelon even exists. But another ally, Australia, has decided not to be so coy.

The man who oversees Australia's security services, Inspector General of Intelligence and Security Bill Blick, has confirmed to the BBC that their Defence Signals Directorate (DSD) does form part of the network.

"As you would expect there are a large amount of radio communications floating around in the atmosphere, and agencies such as DSD collect those communications in the interests of their national security", he said.

But the system is so widespread all sorts of private communications, often of a sensitive commercial nature, are hoovered up and analysed.

Journalist Duncan Campbell has spent much of his life investigating Echelon. In a report commissioned by the European Parliament he produced evidence that the NSA snooped on phone calls from a French firm bidding for a contract in Brazil. They passed the information on to an American competitor, which won the contract.

• Millions Of Cars Have Tiny Black Boxes
• Data On Speed, Braking, Seat Belt Use Collected
• Do They Improve Safety Or Invade Your Privacy?

You know about black boxes. They're the data recorders on airplanes that help investigators solve crashes and help manufacturers improve safety.

But, you probably don't know that something similar may be in your own car. Car makers have equipped millions of automobiles with "event recorders" -- mini-black boxes tucked under the seat or inside the dashboard.

The event recorder is really part of the air bag system. It constantly monitors information - like speed and braking - and when it senses a serious crash, it sends a signal to fire the air bags.

In the General Motors version, the black box also records the last five seconds before a crash, and that information can be downloaded.

The black boxes can tell whether and when the brakes have been applied and whether the driver was wearing a seat belt. That kind of precise information about what happens in a crash can lead to safer designs.

"A black box allows us to understand what happens and so get away from guessing. And when you know, you can do a better job of creating safety performance," said auto safety expert Ricardo Martinez.

Black boxes in cars is not a completely new idea. In London, they are on police cars. And event recorders have been used for years on the racing circuit to enhance safety and fine tune performance. But do you want a black box on your car?

"I would not buy a car that had this kind of capability," said Evan Hendricks, the editor of Privacy Times.

"The problem with all the information that's collected about us is it's only one subpoena away from a law enforcer, a district attorney or your spouse's divorce lawyer," Hendricks said.

It's already happened. Former NFL football player Jerome Brown was killed when his Corvette slammed into a tree. Brown's family sued General Motors, claiming the car's air bag went off prematurely and caused the crash. But GM, using information from that car's black box, proved otherwise and won the case.

The car companies are skittish about privacy concerns and don't like to talk about black boxes. But the safety potential makes the technology appealing, even if it's installed without fanfare, and perhaps even without you knowing about it.

Plenty of people worry about their privacy online, but few consider that someone may be eavesdropping on what they're typing -- through a wall or even across the street. It's something government snoops have been able to do for at least the last decade, according to newly released documents from the U.S. National Security Agency. Spy agencies have dubbed the concept TEMPEST, a code name for technologies used to intercept and decipher the electromagnetic signals that all computers emit. Spooks have known about TEMPEST technologies at least since the 1960s -- some people have even patented ways to shield computers.

But details that aren't classified have been relatively scarce. John Young hopes to change all that. This week he began to publish on his web site the results of TEMPEST documents he obtained from the NSA through a Freedom of Information Act request. ‘People don't know it's out there as a snooping threat,’ says Young, an architect-turned-archivist who collects cryptographic documents. ‘Defense contractors have it but it's under nondisclosure. It's pretty carefully guarded.’

One study -- one of the few that's not classified -- performed by UK researchers Ross Anderson and Markus Kuhn showed that it was possible to capture images from a remote computer monitor. Government-spec shielded systems ward against this, but are more expensive and in limited supply in the private sector...’They're able to do standoff surveillance without tapping,’ said Young. ‘That's the most lethal thing in there.’

The Internet Engineering Task Force has had one guiding principle: To solve the problems of moving digital information around the world. As attendance at meetings swelled and the Internet became a vital portion of national economies, the standards-setting body has become increasingly important, but the engineers and programmers who are members remained focused on that common goal. No longer. Now the IETF is debating whether to wire government surveillance into the next generation of Internet protocols…To reach even a preliminary decision in a special plenary session of the IETF meeting in Washington next month, attendees must weigh whether law enforcement demands are more important than communications security and personal privacy -- a process that places technology professionals in the unusual position of taking a prominent political stand.

’As Internet voice becomes a wider deployed reality, it is only logical that the subject has to come up,’ IETF chairman and Cisco engineer Fred Baker said. ‘We are deciding to bring it up proactively rather than reacting to something later in the game.’ Many governments, including the United States, require telephone companies to configure their networks so police can easily wiretap calls. As more phone calls flow through the Internet, some experts predict that the FBI and similar agencies will demand additional surveillance powers."