The reach of the US and British intelligence agencies encompasses not only those still working for the United Nations like its secretary-general, Kofi Annan, but even those who have retired. Take Hans von Sponek, the former UN diplomat, for example.
Speaking from his home in Geneva last night, Mr Von Sponek said he had strong reasons for believing his phone is being bugged by the US. "I am a small fish in all this," he said. "But I feel uncomfortable at times, without being paranoid."
Mr Von Sponek, a strait-laced Prussian who was based in Baghdad for the UN, is not the kind given to paranoia. But, as a leading campaigner against Iraq sanctions, he has been troublesome to America and Britain and a natural target for the biggest joint intelligence operation in the world.
James Bamford, a specialist in intelligence, said that every 60 minutes the US and British intelligence agencies intercept millions of telephone calls, emails and faxes.
He described the National Security Agency, the US eavesdropping organisation, and its British counterpart, GCHQ, as "the largest espionage organisation the world has ever known, one capable of eavesdropping on conversations virtually anywhere on the planet". Their joint operation is called Echelon.
Mr Bamford, author of Body of Secrets, about how the NSA and GCHQ eavesdrop on the world, and who was given access to both organisations and their officials, said last night of the alleged bugging of Mr Annan: "I am sure they did it."
He added: "They could do it in a number of different ways. They would find out where it [Annan's phone] goes in the New York exchange and do a wire tap. They would want to go into his office if he had an encrypted phone. You would want a receiver for that."
While the CIA and its British partner, MI6, tend to be the better known parts of the intelligence community, it is the NSA and GCHQ that produce the greatest amount of intelligence. The NSA budget and staff levels far exceed those of the CIA.
There is plenty of evidence showing that in recent years the NSA and GCHQ have listened to enemies, European allies and neutral countries. A leaked NSA memo shows they targeted six swing countries on the UN security council in the run up to the Iraq war last year. At least two of those countries have confirmed they were bugged. At the same time, according to the former cabinet minster, Clare Short, the office of Mr Annan was also bugged.
The bulk of the intercepts by the NSA and GCHQ are pulled down from the ether by powerful listening posts round the world. A British listening post in Cyprus is capable of hearing a plane land at the airport in Beijing, according to a visitor to the Mediterranean site.
But the old ways are just as effective. Bugs are planted in the offices and homes of targets by agents posing as cleaners, photocopy engineers and other near invisible staff. They are often placed behind light fittings or plugs.
The UN believes this is possible at its offices. Mr Annan's spokesman, Fred Eckhard, told a press conference yesterday that there were regular sweeps of the secretary-general's office to check for any bugs. An electronic machine, not much bigger than a briefcase, can be set up in a room to detect any electronic covert devices.
Mr Bamford said that the US has form on bugging the UN. When the US hosted negotiations on the setting up of the UN in San Francisco in 1945, the US listened in on all the delegations, especially the French who had a complex six-wheel cipher machine but one that the US codebreakers were able to read.
Mr Bamford claims part of the reason the US wanted the UN on its soil was to accommodate the eavesdroppers of the NSA.
He said that normally the US has responsibility for the UN while Britain has responsibility for western Europe. He added that they were one and the same organisation. Listening posts were once spread round Europe but Mr Bamford said the bulk of the European operations had been transferred to GCHQ in England.
International law prohibits operations such as those allegedly mounted against the UN - whether the six members of the security council or the possible bugging of Mr Annan's office or the suspicious Mr Von Sponek - but it is frequently flouted. In theory, the 1961 Vienna convention on diplomatic relations states that the premises of a diplomatic mission "shall be inviolable", and agents of the host state cannot enter without permission.
There is general assumption within the diplomatic world that there is a strong risk of being bugged. During construction or refurbishment, whether the British embassy in Moscow or the Pakistan high commission in London, attempts will be made to infiltrate listening devices.
Thousands of bugging devices are sold in Britain each year. They can be bought for as little as £100 by husbands or wives suspicious of their partners, or more expensive devices by businesses seeking competitive advantages over rivals. But these pale into insignificance compared to the sophistication and cost of the operations mounted by the US and British governments.
On the other end of such operations are people like Mr Annan and Mr Von Sponek. The latter was the UN humanitarian coordinator of Iraq for 18 months, leaving Baghdad in 2000. He witnessed the suffering of the Iraqis and blamed much of it on the sanctions regime, which made him unpopular with the US and British governments.
He said last night: "The phone has a strange echo but that may not prove much. The Swiss authorities say it is not them."
He said he received a warning from a friend that his phone was being bugged. Asked how he could prove this, the friend told him of a call he had made to Amman in Jordan and what he had said. That convinced Mr Von Sponek. He said the same friend informed him that he was being monitored from a US base in Stuttgart.
Mr Von Sponek said: "It is too bad but it is upsetting."