If the American intelligence services rely on tapping phones and on emails in computers, fax messages and so on, they're in big trouble. Reasonable intelligence services have a thousand and one more successful and confidential ways to capture a word here, a word there, from the people who know something.
The basic assumption of anyone working in the Prime Minister's Office, the Defense Ministry, the chief of staff's bureau and other offices is that every single word that goes out through the phone, computer and fax is subject to wiretapping, often by more than one intelligence service. Sometimes half a dozen intelligence services "sit" on one telephone line.
The people at the top ranks of the government are usually experienced and cautious about what they say. The different intelligence services try to capture the words of those who forget to be careful or who don't know how to be careful. And there are few of those, relatively. Experience is what prevents leaks, unless they are intentional. Often a person will talk on the phone knowing that he is being eavesdropped, and wanting to convey an indirect message to the listeners.
In the dangerous bureaus in terms of leaking classified information there is strict compartmentalization. People don't talk, both in order to accumulate knowledge – and knowledge is power – and in order to "impress" their surroundings. How can access to information be limited to people who work 24 hours a day within several adjacent rooms? If the person limiting the access is experienced, there is no problem. People are careful not only on the telephone, but also of each other.
The frequent wiretapping pricks up the ears in face-to-face conversations. Leaders who meet usually listen carefully, with almost absolute attention, to what they hear. From this they learn what the leader facing them has learnt about them, and the perceptive ones among them can even observe the intelligence leaks and bugging which have made it to the other leader's ears.
An Israeli emissary who once met with another country's foreign minister heard him say several words which the emissary had said the night before at the Israeli ambassador's home. He went back to the Israeli ambassador and told him: Your house is being bugged. The ambassador alerted the suitable security officials from Israel, and they found tiny microphones planted in his home and in the garden too.
The "garden stories" are part of the folklore of the Israeli security services: According to one of the stories, during the Camp David summit in the early 1980s, Menachem Begin and his people would go deep into the grove and talk there to avoid eavesdropping. But there, between the trees, awaited them the microphones of the American intelligence agency. Israeli media also reported about the businessman whose house phone had been cut off, forcing him to go out to a payphone near his home. The listening devices were planted in that exact telephone booth.
This doesn’t mean that information is not collected from telephone conversations. Leaders are usually in a hurry to discuss different issues, they don't have time, and they're sometimes not careful. A lot of information can also be found in gossip shared in phone conversations. But the important and confidential things are conveyed through different and diverse methods, which this is not to place to discuss. You won't find the big secrets on the phone.