The China based hacker group which attacked Google in 2009, has launched hundreds of other cyber assaults since then, concentrating on US defense companies and human rights groups, according to new research from Symantec.

In January 2010, Google had threatened to end its operations in China after a cyber attack targeted Chinese human rights activists.

About 20 other organisations were also targeted in the cyber attack later dubbed Operation Aurora from China-based hackers who have reported to have stolen the intellectual property.

The hackers were never publicly identified and the cyber attacks against US institutions originated from China raised tensions between Washington and Beijing.

Symantec research group manager Eric Chien said that it was big news at the time, but what people don’t realise is that this is happening constantly.

"They haven’t gone away, and we wouldn’t expect them to go away," Chien said.

Symantec said that the hackers behind Operation Aurora have concentrated on stealing design documents from defense contractors and their suppliers which include shipping, aeronautics, arms, energy, manufacturing, engineering as well as electronics companies.

The hackers used components of a common infrastructure that Symantec termed the "Elderwood Platform".

Symantec said that the second most common group of targets was non-government organisations involved in Tibetan human rights issues and financial firms as well as software companies were also targeted.

Symantec claims that the Elderwood hackers alone have used eight zero-day vulnerabilities from 2010 to 2012, which is the largest number it has seen from a single organisation.