President Barack Obama last week announced the introduction of curbs on the use made by US intelligence agencies of communications data they have collected from private individuals, government leaders and organisations around the world. Obama’s move was denounced by civil rights defenders as a weak and minimal response to the unbridled mass espionage practices of the National Security Agency (NSA), revealed to the media by its former contractor Edward Snowden. Among the most startling of these was the recent revelation that the NSA had successfully infiltrated a submarine civil communications cable that runs from France to the Far East, in which it planted a virtually undetectable parallel network to spy on the traffic that passes through it. French telecoms giant Orange, part of the consortium that uses the cable, has told Mediapart it will this month file legal action over the hacking, opening the path for a judicial investigation that could have major political and diplomatic consequences. As Jérôme Hourdeaux reports, the technique used by the NSA to attack the cable is one of the most fearsome mass espionage systems yet uncovered.