China is suspected of interfering with two U.S. government satellites in one of its most advanced hacking operations to date.

On four occasions between 2007 and 2008 Chinese agents are said to have breached security on the environment-monitoring craft.

The last hack was so effective that they could have completely taken control of the satellite, but did not do so.

A Landsat-7 earth observation satellite system experienced 12 or more minutes of interference in October 2007 and July 2008.

Hackers also interfered with a Terra AM-1 earth observation satellite twice, for two minutes in June 2008 and nine minutes in October that year.

During the final hack ‘the responsible party achieved all steps required to command the satellite’, but did not do so.

Both craft use the commercially operated Svalbard Satellite Station in Spitsbergen, Norway, that ‘routinely relies on the Internet for data access and file transfers,’ the commission said, indicating this might have been how they were attacked.