How phonebook-scraping apps work
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Hands-on with a phone number harvesting app

Three mobile phone apps that help users block spam calls have been building up searchable databases of people's names and phone numbers - sometimes without their permission.

A report from Hong Kong investigative news agency Factwire found that apps CM Security, Sync.ME and Truecaller have built up databases with billions of people's phone numbers - including top politicians in Hong Kong and the UK.

The apps let users "reverse look-up" calls from numbers they do not recognise - but take much of their data from users' contact lists.

CM Security says it has temporarily halted its "reverse look-up" function to address privacy concerns, while Sync.ME and Truecaller say people can opt out from their databases via their websites.

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Reporting by the BBC's Helier Cheung in Hong Kong

  • 25 Nov 2016