North Korea's main spy agency has a special cell called Unit 180 that is likely to have launched some of its most daring and successful cyber attacks, according to defectors, officials and internet security experts.North Korea has been blamed in recent years for a series of online attacks, mostly on financial networks, in the United States, South Korea and over a dozen other countries.
Cyber security researchers have also said they have found technical evidence that could link North Korea with the global WannaCry "ransomware" cyber attack that infected more than 300,000 computers in 150 countries this month. Pyongyang has called the allegation "ridiculous".
