The TV chef says some 13 to 14-year-olds share "porno sort of" photos which he finds "frightening".
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Russian twitter accounts posted more than 45,000 messages about Brexit in 48 hours during last year's referendum.
The Facebook account for viral news website Unilad has been deleted.
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Rozina Sini
BBC News
The Pentagon has deleted a post it retweeted in error that called for President Trump to resign.
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The online talent network said it wanted to focus its investment elsewhere.
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The failure of a 4chan prank shows how the extremist site's influence is on the wane.
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Sherie Ryder
BBC News
When Iraq and Israel beauty contestants posted a photo together on social media, reaction was very mixed.
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BBC Trending
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Various social media accounts claim to represent the ruling party of Zimbabwe. It is far from clear which do.
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Prince William worked with tech firms, charities and parents to come up with a code of conduct.
Read moreShe's still in primary school, but Amoy Antunet has big ambitions - and plenty of scientific equipment