American federal agencies were breached more than 46,000 times last year, according to figures released by the US Computer Emergency Readiness Team (US-CERT).

Documents obtained by the Associated Press (AP), following a freedom of information request, showed that attacks had risen from 27,000 in 2009, with the US-CERT responding to a quarter of a million incidents in 2013 alone.

Eric Rosenbach, assistant secretary of defence for Homeland Defence and Global Security, told the Associated Press (AP): "No matter what we do with the technology … we’ll always be vulnerable to the phishing attack and…human-factor attacks unless we educate the overall workforce."

A White House review of federal breaches last year blamed half of the problems on employees, with a fifth of leaks attributed to work policy violation, 16% to devices being stolen and 12% to sensitive information being mishandled after printing.

On rare occasions workers intentionally leak information, as was the case with the former National Security Agency (NSA) agent Edward Snowden, who disclosed vast amounts of information on American and British spying activities.

In the past Chinese and Russian hackers have been frequently accused of attacking American companies and networks, often looking to steal intellectual property or engage in cyber-espionage.