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Major cyber security firms Symantec Corp and Kaspersky Lab said on Monday they were looking into clues that may connect last weekend’s global cyber attack known as WannaCry with programs previously attributed to North Korea, Reuters reported.

The two companies said some code in an earlier version of the WannaCry ransomware, which has encrypted data on hundreds of thousands of computers since Friday, and demanded users pay money to regain control of their machines, had also appeared in programs used by the Lazarus Group, which researchers from many companies said is run by North Korea.

Initial reports said that 74 countries were hit by the WannaCry attack, but updated numbers on Sunday indicated the attack affected about 200 thousand victims in approximately 150 countries.

North Korea was identified as being responsible for a 2014 cyber attack on Sony Pictures.

In that attack, North Korean-backed hackers broke into Sony's servers, published private emails and information and threatened to attack movie theaters screening "The Interview," a comedy film about an assassination plot on North Korean leader Kim Jong Un.

The attack and the threats eventually led Sony to announce it was cancelling its planned release of “The Interview”.

The North Korean mission to the United Nations was not immediately available for comment regarding the WannaCry attack.