“Mr. Trump’s aides have repeatedly warned him that his cellphone calls are not secure, and they have told him that Russian spies are routinely eavesdropping on the calls, as well. But aides say the voluble president, who has been pressured into using his secure White House landline more often these days, has still refused to give up his iPhones. White House officials say they can only hope he refrains from discussing classified information when he is on them. ...

”The issue of secure communications is fraught for Mr. Trump. As a presidential candidate, he regularly attacked his Democratic opponent, Hillary Clinton, during the 2016 campaign for her use of an unsecured email server while she was secretary of state, and he basked in chants of ‘lock her up’ at his rallies.“

— from the article, ”When Trump Phones Friends, the Chinese and the Russians Listen and Learn," in The New York Times