US Congress briefed on hacker attack

New York

FOR more than five years, US intelligence agencies followed several groups of Chinese hackers who were systematically draining information from defence contractors, energy firms and electronics makers, their targets shifting to fit Beijing's latest economic priorities.

But last summer, officials lost the trail as some of the hackers changed focus again, burrowing deep into US government computer systems that contain vast troves of personnel data, according to US officials briefed on a federal investigation into the attack and private security experts.