Computer codes are often shared among different groups, so the matching code isn't definitive proof Lazarus was behind the cyberattack.
Though North Korea has never admitted any involvement in the Sony Pictures hack, security researchers and the USA government are confident in the theory and neither can rule out the possibility of a false flag.
But in vain. White House Homeland Security adviser Tom Bossert told reporters, "We are not aware of payments that have led to any data recovery".
Security officials around the world expressed relief as the spread of the virus seemed to slow its pace, though not before freezing files and demanding ransom from the operators of hundreds of thousands of computers in at least 150 countries, including the United States.
The attack includes elements that belong to the U.S. National Security Agency and were leaked online last month. They pointed to how easy it was to stop and how little money it has collected so far - a little over $50,000, a relatively paltry amount for an attack so large.
Some suspect a group known as Lazarus, believed to be a mixture of North Korean hackers operating in tandem with Chinese "cyber mercenaries".
There is another possibility that "Lazarus Group" may be working independently and without the instructions from North Korea, the report added. "It is similar to North Korea's backdoor malicious codes", said Choi. The 2014 Sony hack was also pinned on the hacker collective.
Choi said that if North Korea's culpability is proven, the world should start taking their capabilities seriously and ensure consequences for such actions.
The North Korean mission to the United Nations could not be reached for comment, while the Federal Bureau of Investigation declined to comment.
More than 200,000 computers were crippled worldwide, the paper said, citing the European Police Office.
Some experts see the latest attack as an anomaly. Taiwan Power Co. said that nearly 800 of its computers were affected, although these were used for administration, not for systems involved in electricity generation.