Security firms claim they’ve found links between WannaCry and malware used by Lazarus Group. Lazarus Group is the codename given to a group of hackers responsible for the Sony hack, SWIFT bank attacks, and other financial institutions hacks. Security firms say they’ve also found a similar SSL implementation in the Brambul backdoor, another of Lazarus Group’s hacking tools. The companies make these connections based on some very skimpy claims, so they should not be taken as universal or conclusive proof that North Korea developed and released the malware.
Source: https://www.bleepingcomputer.com/news/security/3-security-firms-say-wannacry-ransomware-shares-code-with-north-korean-malware/