On September 12 2001, staff at the US National Security Agency translated a phone call made two days earlier by a suspected al-Qaeda operative. It said: ‘Tomorrow is zero hour.’
Was this the vital clue that could have averted the Twin Towers attack? As the world marked the first anniversary of the 9/11 strike this week, the questions were again being asked: should plans for this act of terrorism have been detected? Can future attacks be forestalled?
In theory the US has access to the technology to monitor communications from phone calls and radio transmissions to e-mails worldwide, and the computing power to analyse the results. So what went wrong?
Tracking small terrorist cells in a world of six billion people is a monumental task. According to a report by the International Telecommunications Union, international telephone traffic alone stood at 100 billion minutes in 1999. The US monitors communications by a highly secret global system of surveillance using satellites, ground stations and computers. Usually known as Echelon (though this is believed to be the name of a software search engine used to analyse the data), it has its roots in the 1948 UK/US Agreement, the existence of which was also officially denied for many years.
Echelon’s existence was confirmed to security historian Prof Christopher Andrew of Oxford University by Dr Louis Torella, a NSA deputy director in the 1980s. The NSA is the US government’s collator of ‘signal intelligence’ and costs taxpayers $7bn (£4.5bn) a year – twice as much as the CIA.
The UK/US Agreement, based on wartime co-operation, included Australia, New Zealand and Canada. Listening stations around the world and in orbit were the result. Since the first transatlantic radio transmission in 1901 many communication techniques have been developed. These can use fixed cables and optical-fibre links on land or under the sea; high-frequency radio which bounces off the Earth’s ionosphere to reach places over the horizon; microwave radio relay, a point-to-point system of transmitters and receivers; and communication satellites. All these can now be intercepted.
For undersea cables a ‘tapping pod’ can be attached to detect signals by induction. Optical fibres can be tapped at the opto-electronic ‘repeaters’ where the light signal is reamplified.
Microwave radio, though used to transmit messages site to site, can be intercepted by satellite, a function carried out by a group of satellites operated from an MoD site at Menwith Hill in North Yorkshire. Since the 1980s this station has monitored Middle Eastern networks, among other things and was involved in supporting Desert Storm.Another constellation of satellites, Orion, can pick up signals from VHF radios, cellular mobile phones, paging signals, mobile data links, telemetry and UHF signals. Since 1990 the ground stations for them, based at Menwith Hill, Bad Aibling in Germany, Pine Gap in Australia and Buckley Field in Colorado have all been expanded.
Data from orbiting communication satellites can be intercepted by a handful of strategically placed dishes. The Agreement is known to have established such ground stations in Australia, Japan, New Zealand, Puerto Rico, the US and the UK – again at Menwith Hill and also at Morwenstow, in Cornwall. These stations also have vast antennae to pick up the many high-frequency signals bounced off the ionosphere from all around the world. Medium and long-wave transmissions, which cannot travel beyond the horizon, need to be detected using local land, sea or air-based systems such as listening posts in embassies or spy planes (or ships).
Being able to intercept communications is only part of the story, however. Filtering and analysing the vast quantities of data produced is the real challenge for the intelligence services. Former NSA director William Studeman reportedly said in 1992: ‘An intelligence collection system alone can generate millions of inputs per half hour. The filters throw away all but 6,500, then only 1,000 meet the forwarding criteria, 10 are selected by analysts and one report is produced.’
Given this, computers are the key to mining the nuggets of information that could save lives. These computers are far more powerful even than the CAD workstations in the design offices of top engineering firms. According to a 1996 paper by the Federation of American Scientists, the intelligence services were using Cray supercomputers. But even these are now old technology. Today signal intelligence analysts use computers powerful enough to simulate nuclear explosions. Researchers who preferred not to be named told The Engineer that IBM’s ASCI White supercomputer is the one used for monitoring communications. It performs calculations at a speed of up to 12 teraflops – the equivalent to the computing power of 12,000 high-end PCs linked together.
Software such as Echelon can trawl the internet and read e-mails and faxes. According to Prof Alan Bundy, an artificial intelligence expert at the University of Edinburgh, ‘Reading e-mail is standard, GCHQ does it routinely and so does the NSA. There’s even an informal campaign by some e-mail users to defeat it by deliberately including lists of key words in innocent e-mails.’
Though his view is disputed, Bundy also believes that speech-recognition technology is in widespread use by GCHQ and the NSA: ‘Speech recognition is now routine, with products for home and office use. It’s far from 100 per cent accurate, but it’s good enough for this kind of monitoring, especially if you have access to the fastest machines in the world – which they do.’
Dr Alan Clark, a research scientist at Carnegie Mellon University’s Language Technology Institute, is working on speech technology. ‘With key words speech recognition is hard but possible – and it could even translate some words. But voice recognition of an individual is still really tough.’
Even if Osama bin Laden is in hiding near the Afghan border and using the public phone network, Clark believes the secret services could not identify him. ‘But I understand he speaks a particular Saudi dialect. They could maybe pick him up from that.’
Other reports suggest, though, that voice-recognition technology advanced enough to identify individuals has been useful in the fight against al-Qaeda. James Bamford, author of books on signal intelligence and a visiting professor at Berkeley’s Goldman school of public policy, even publicised bin Laden’s satellite phone number – but he had stopped using it in 1998.
Whatever the true details of equipment available to the intelligence agencies, the question still remains: with their surveillance expertise, why was there no warning? The answer is staffing levels. The US public has been told that the NSA and CIA don’t have enough linguists for translation duties.
Heads may roll because of that but budgets won’t be cut. The imperative to succeed will ensure more money is invested in anti-terrorist technology. If there is a next time, the US knows it cannot afford to let even one phone call slip through the technological net.