The United States on Friday backed up its allegation that North Korea's leadership was behind the hacking of Sony Pictures by announcing new, if largely symbolic, economic sanctions against 10 senior North Korean officials who the US authorities said was the source of ''many of North Korea's major cyber-operations.''
The actions were based on an executive order President Obama signed on vacation in Hawaii, as part of what he had promised would be a ''proportional response'' against the country. But, in briefings for reporters, officials said they could not establish that any of the 10 officials had been directly involved in the destruction of much of the studio's computing infrastructure.
In fact, most seemed linked to the North's missile and weapons sales. Two are senior North Korean representatives in Iran, a major buyer of North Korean military technology, and five others are representatives in Syria, Russia, China and Namibia.
The sanctions are a part of the response to the cyber attack on Sony, which was targeted as it prepared to release 'The Interview,' a crude comedy about a CIA plot to kill North Korea's leader Kim Jong-un.
The administration has said there would be a covert element of its response as well. Officials sidestepped questions about whether the United States was involved in bringing down North Korea's internet connectivity to the outside world over the past two weeks.
Perhaps the most noticeable element of the announcement was the administration's effort to push back on the growing chorus of doubters about the evidence that the attack on Sony was North Korean in origin.
Several cyber security firms have argued that when Obama took the unusual step of naming the North's leadership - on 19 December the president declared that ''North Korea engaged in this attack'' - he had been misled by American intelligence agencies that were too eager to blame a long-time adversary and allowed themselves to be duped by ingenious hackers skilled at hiding their tracks.
While the sanctions will have limited effect, as North Korea already is under tough US sanctions over its nuclear programme, American officials portrayed them as a swift, decisive response to North Korean behaviour they said had gone far over the line. Never before has the US imposed sanctions on another nation in direct retaliation for a cyber-attack on an American company.
"The order is not targeted at the people of North Korea, but rather is aimed at the government of North Korea and its activities that threaten the United States and others," US President Barack Obama wrote in a letter to leaders in Congress.
The sanctions also apply to three organisations closely tied to North Korea's government: the country's primary intelligence agency, a state-owned arms dealer that exports missile and weapons technology, and the Korea Tangun Trading Corp, which supports defense research. All three entities were already subject to US sanctions.
Obama has also warned Pyongyang that the US is considering whether to put North Korea back on its list of state sponsors of terrorism, which could jeopardise aid to the country on a global scale. Beyond that, it's unclear what additional penalties the US has available.
North Korea has denied involvement in the cyber-attack, which led to the disclosure of tens of thousands of confidential Sony emails and business files, and then escalated to threats of terrorist attacks against movie theatres. Many cyber security experts have said it's possible that hackers or even Sony insiders could be the culprits, and questioned how the FBI can point the finger so conclusively.