Donald Trump's mobile phone use worries former Obama tech officer

"Andrew McLaughlin, former deputy chief technology officer for the Obama administration, said the vulnerabilities were a concern.

"What we ended up with was a military-grade, encrypted phone that had the microphone ripped out," Mr McLaughlin said, adding that he thinks the White House communications office has prevailed upon Mr Trump to use some kind of phone with enhanced security.

He suggested one with strong encryption, disabled location services and one that talks with a military network instead of commercial cell services.

Mr McLaughlin also said it's possible that the number Mr Trump is giving to world leaders rings to someone else's phone, who then transfers the call to the President, a system that could protect Mr Trump from anyone trying to monitor his communications."