The US government named three entities, including North Korea's military intelligence agency, and sanctioned 10 people with links to weapons sales and proliferation.
“It’s not as if they travel a lot abroad to western Europe or the United States ... They don’t have billions of dollars in western banks,” said Joel Wit of 38North, part of the US Korea Institute at Johns Hopkins University in Washington.
Pyongyang has denied involvement in the cyberattack. Washington said there was no evidence that any of the three entities or the individuals were linked to it, Reuters reported.
Treasury Secretary Jacob J. Lew said in a statement that Washington had a "commitment to hold North Korea accountable for its destructive and destabilizing conduct."
Lew said that even as a probe by the FBI continued "these steps underscore that we will employ a broad set of tools to defend US businesses and citizens, and to respond to attempts to undermine our values or threaten the national security of the United States."
The cyberattack that crippled Sony's networks occurred as the company was preparing to release the film "The Interview," a comedy centered on plans to assassinate North Korea's leader Kim Jong Un.