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Telephone tapping is strictly controlled in many countries to safeguard an individual's privacy. Telephone tapping often needs to be authorised by a Court, and is normally only approved when evidence shows it is not possible to detect criminal or subversive[?] activity in less intrusive ways. Illegal or unauthorised telephone tapping is often a criminal offence.
There is nothing illegal about one of the parties to a telephone call recording the conversation, or giving permission for calls to be recorded or permitting their telephone line to be tapped. Many businesses record their telephone calls for legal reasons, so that they can prove what was said, train their staff, or monitor performance. This activity is not normally considered telephone tapping because it is done with the knowledge of at least one of the parties to the telephone conversation. Some advise or even ask if a conversation can be recorded.
When telephone exchanges were mechanical a tap had to be installed by technicians, linking circuits together to route the audio signal from the call. Now that many exchanges are being converted to digital technology installing taps is far simpler, and can be done by installing small plugs, or even by computer. Telephone services provided by cable TV companies are tapped in a similar way.
Unless the tap has been very badly installed, it is not possible to tell if your line is being tapped or not. The noises that some people believe to be telephone taps are really just noise created by the induction of signals from other phone lines. Because the tap is made at the exchange it is very difficult to tell if the line is tapped because there will be no appreciable difference in volume. But irrespective of the tapping of content, communications data will always be collected automatically, and stored for later use by the billing department of your phone company or the security services.
For telephone services run via digital exchanges, the information generated will consist of a list of the phone numbers you have called, the duration of the calls, and perhaps a log of the type of communications media being used (some services send data and voice communications via different routes to conserve bandwidth).
It's also possible to be tap conversations unofficially. There are a number of ways to monitor telephone conversations:
To guard against unofficial line taps you should know where your telephone line runs, and perhaps inspect it regularly for new joins, or small wires connected to the line.
Mobile phones are, in surveillance terms, a major liability. This liability will only increase as the new third-generation (3G) phones are introduced. This is because the base stations will be located closer together.
For mobile phones the major threat is the collection of communications data. This data not only includes information about the time and duration of the call, but also the geographical location where the call was made from and to whom. This data can be determined generally because the geographic communications cell that the call was made in is stored with the details of the call. But it is also possible to get greater resolution of a persons location by combining information from a number of cells surrounding the persons location. This additional precision must be specifically enabled by the telephone company - it is not part of ordinary operation. There is no counter-measure against the state/telephone companies doing this.
The old first generation mobile phones could be easily monitored by anyone with a 'scanning all-band receiver' because the system used an analogue transmission system - like an ordinary radio transmitter. The second generation digital phones are harder to monitor because they use a digitally compressed transmission. However the state can tap mobile phones with the co-operation of the phone company. It's also possible for organisations with the correct technical equipment, such as large corporations, to monitor mobile phone communications and decrypt the message. There were proposals for European mobile phones to use stronger encryption, but this was opposed by a number of European states.
Mobile phones can be used anonymously, but it is very expensive to do. Pre-paid mobile phones can be bought without having to give details of your name or address, and because you insert cards there is no billing information. However, once you have been identified as using a certain phone, you can be tracked. So if you require longer-term anonymity it is necessary to regularly change the phone every few days.