With regard to the letter entitled ‘Hang up’ (September 10), the calls described are almost always what are known as Wangiri calls. Wangiri is Japanese for ‘one ring and cut’.

The idea is that the incoming call cannot be answered because it rings for such a short period of time that most people cannot answer the call quickly enough (actually 10-15 per cent are answered because so many people are using their mobiles for other things such as internet browsing and see instantly the incoming call but this is seen as a ‘cost of doing business’ by the criminals making the calls as they have to pay for the answered calls) and only a missed call notification is seen.

When the called party (almost always a mobile user) sees the missed call, approximately 15 per cent of users call the number back thinking they have a genuine missed call. The calling number is a high-cost international premium rate number.

The criminals who are making the calls (in most cases the criminals have automated software making the calls) are renting the numbers that are called back and are paid a commission for all calls to these high-cost numbers.

This is a growing problem across a number of countries.

Do not call back numbers you do not recognise. Pay special attention to any number you do not recognise.

In many cases it is not just criminal fraudsters who are making money from this but serious level terrorist groups.

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