Analysis The cause and perpetrators behind interference against two US scientific satellites remains unknown to American military commanders more than three years after the mysterious event.

The Congressional US-China Economic Security and Review Commission said in its latest annual report that two US-maintained environment-monitoring satellites experienced interference at least four times in 2007 and 2008. Draft versions of the dossier, seen prior to the publication of the completed report last Wednesday, suggested the interference came from a ground station in Spitsbergen, Norway, and paints China as the chief suspects behind the presumed attacks.

However the satellite services firm running the ground station told El Reg that there's no evidence of any attack against its systems. Separately the commander of US military space operations said that insufficient evidence made it impossible to confidently attribute blame over the possible attempts to take control of the Landsat-7 and Terra AM-1* satellites, which are both managed by NASA.

"The best information that I have is that we cannot attribute those two occurrences," said General Robert Kehler, commander of the U.S. Strategic Command, Reuters reports. "I guess I would agree that we don’t have sufficient detail."

Kehler made his comments during a conference call on cyber and space issues.

Earlier drafts of the commission's report traced the cause of the probe interference to the Norwegian ground station owned and run by Kongsberg Satellite Services (KSAT), which denied any occurrence of interference via its facilities. In response to queries by El Reg, the satellite services issued a statement saying a thorough investigation has turned up nothing amiss. Neither NASA, which maintains the satellites, nor regulators at the National Oceanic and Atmospheric Administration had complained, it added

The statement read:

KSAT has not experienced any attempt to enter into the company’s systems from outside sources. Furthermore, KSAT does not have any indication that hacking of satellites using the KSAT Svalbard station has taken place. A careful screening of our security systems has not indicated any attempts to access SvalSat from unauthorized sources. We have not received any message from NASA that their satellites were hacked. To our knowledge, NASA has not observed any external, unauthorized access to their satellites. The internet is occasionally used for distribution of x-band payload data received from the satellites to the end user. Hence, this communication channel cannot be an access point for unauthorized access if it had happened. Due to the layout of our communication systems it is not possible to access any NASA satellites from KSAT sources. The US government, represented by NOAA, regularly inspects KSAT operation. Irregular activity has not been observed nor reported.

References to KSAT and Svalbard were removed from the commission's final report because, according to a KSAT spokesman, the hacking allegations were "unsubstantiated and no evidence has been found".

Despite this, the congressional committee report continues to argue that interference against the US satellites remains a threat. It says Chinese military doctrine advocates the use of techniques for disabling an enemy's ground-based satellite control facilities during a time of conflict.

China is now among the top few space powers in the world. China’s leadership views all space activities through the prism of comprehensive national power, using civil space activities to promote its legitimacy in the eyes of its people, to produce spin-off benefits for other industries, and for military-related activities. For example, China appears to be making great strides toward fielding regional reconnaissance-strike capabilities. China has also continued to develop its antisatellite capabilities, following up on its January 2007 demonstration that used a ballistic missile to destroy an obsolete Chinese weather satellite, creating thousands of pieces of space debris. As a result, in April 2011, astronauts evacuated the International Space Station out of concern of a possible collision with this debris. In addition, authoritative Chinese military writings advocate attacks on space-to-ground communications links and ground-based satellite control facilities in the event of a conflict. Such facilities may be vulnerable: in recent years, two U.S. government satellites have experienced interference apparently consistent with the cyber exploitation of their control facility.

The report says links between supposedly secure control networks and the internet offer a soft underbelly that's open to attack.

Malicious actors can use cyber activities to compromise, disrupt, deny, degrade, deceive, or destroy space systems. Exploitations or attacks could target ground-based infrastructure, space-based systems, or the communications links between the two. Authoritative Chinese military writings advocate for such activities, particularly as they relate to ground-based space infrastructure, such as satellite control facilities. Satellites from several U.S. government space programs utilize commercially operated satellite ground stations outside the United States, some of which rely on the public Internet for "data access and file transfers," according to a 2008 National Aeronautics and Space Administration quarterly report. The use of the Internet to perform certain communications functions presents potential opportunities for malicious actors to gain access to restricted networks.