I remember watching a documentary on the BBC about the British Army relatively recently (i.e. within the last two to three years). One unit was being deployed to Estonia on exercise and there was a scene in the programme where the troops were explicitly told not to take their personal mobile phones as the Russians would try and hack into them.
There’s a story about it here (yeah, I know, it’s the Daily Mail so apologies in advance. Similar stories are in the Daily Telegraph and the Wall Street Journal but they’re behind pay walls)
https://www.dailymail.co.uk/news/art...ellphones.html