[ghaff]

From that article it seems like it's the kid who assumed it was the WiFi that caused the leak.

'But I was using the data on my phone and they were using the Wi-Fi at Gatwick and so the message was picked up by the security people.'

As far as I know, it doesn't seem like anyone in the UK has said where they got the info from. And the Daily Mail may just be assuming the kid's right and is jumping to a conclusion.