What does the FBI want Apple to do?

Apple will contest a court order to help FBI investigators access data on a phone used by San Bernardino gunman Syed Rizwan Farook.

The company had been ordered to help the FBI circumvent security software on Farook's iPhone, which the FBI said contained crucial information.

In a statement, Apple chief executive Tim Cook said: "We oppose this order, which has implications far beyond the legal case at hand."

The BBC's Technology reporter Chris Foxx explains what the FBI wants Apple to help them with.