North Korean hackers have carried out a systematic effort to target financial institutions all over the world. Their methods are bold, though not always successful. In their most profitable operations, they have manipulated how major financial institutions connect to the international banking system. By tricking components of this system into thinking their hackers are legitimate users, they have enabled the transfer of tens of millions of dollars into accounts they control. They have tampered with log files and bank transaction records, prompting a flurry of security alerts and upgrades in international financial institutions. Most publicly, and perhaps by accident, the hackers have disrupted hundreds of thousands of computers around the world in a ham-fisted effort to hold valuable data for ransom. Through their successes and failures, they learned to modify and combine their tricks, evolving their operations to be more effective.
Read more about it: https://www.wired.com/story/how-north-korea-robs-banks-around-world/