Rede Record, a Brazilian television network, visited the farm in June and could find nobody who had heard of Ms Precht.

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Kallasvuo's predecessor, Jorma Ollila, visited U.S. network honchos perhaps once every three or four months.

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The US-based social network said that the attack occurred when employees visited a mobile developer website "that was compromised".

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Facebook may be the most widely-used social network, but Google is still the number one visited website attracting over 1 billion visitors per month.

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