Beijing on Friday rejected an AFP report that Chinese hackers were suspected of being behind a series of cyber attacks on European aerospace giant Airbus.
The hackers targeted Airbus suppliers -- British engine-maker Rolls-Royce, French technology consultancy and supplier Expleo, and two other French contractors -- in search of commercial secrets, according to security and industry sources who spoke to AFP on condition of anonymity.
None of the sources who spoke to AFP could formally identify the perpetrators of the attacks, pointing to the extreme difficulty in obtaining evidence and identification.
Many state-backed and independent hackers are known to disguise their tracks, or they may leave clues intended to confuse investigators or lead them to blame someone else.
But the sources said they suspected Chinese hackers were responsible, given their record of trying to steal sensitive commercial information and the fact that Beijing has just launched a plane designed to compete with Airbus and US rival Boeing.
"In recent years, there have been many reports about cyber attacks in the media. In these reports, without any evidence, the parties concerned always pin the label of cyber attack on China and smear China," foreign ministry spokesman Geng Shuang said at a regular press briefing.
"This practice is neither professional nor responsible, and even has ulterior motives," Geng said, adding that China "is a firm defender of network security."
Several sources said they believed a group of hackers linked to the Chinese Communist Party, known as APT10, could be behind the attacks.
The United States considers APT10 to be state-backed hackers linked to the Chinese intelligence services and military.
But another source pointed to another group of Chinese hackers known as JSSD, which are believed to operate under the regional security ministry in the coastal province of Jiangsu.
AFP spoke to seven security and industry sources, all of whom confirmed a spate of attacks in the past 12 months but asked for anonymity because of the sensitive nature of the information they were sharing.
Two security sources involved in investigating the hacking said there had been four major attacks.
Airbus has long been considered a tempting target because of the cutting-edge technologies that have made it one of the world's biggest commercial plane manufacturers, as well as a strategic military supplier.
In January, it admitted to a security incident that "resulted in unauthorised access to data", but people with knowledge of the attacks outlined a concerted and far bigger operation over the last year.
According to several of the sources, the hackers appeared to be interested in technical documents linked to the certification process for different parts of Airbus aircraft.
They also said that several stolen documents were related to the innovative turbo-prop engines used on the Airbus military transport plane A400M.
One of the sources said the hackers were also interested in the propulsion systems for the Airbus A350 passenger jet, as well as its avionics systems controlling the plane.
