North Korea operatives have sought to use U.S. technology and social media networks to evade U.S.-led sanctions and generate income, taking advantage of many of the same shortcomings that allowed Russians to interfere in the 2016 election.

Cloaking their identities, the North Koreans have been able to advertise jobs and find clients on job-search exchanges such as Upwork and Freelancer.com. They have developed software using the Microsoft-owned site Github, communicated over the Slack messaging service and asked for payments...