The U.S. announced new sanctions against North Korea Thursday, targeting two companies in China and Russia and a North Korean individual.

The Treasury Department said that it blacklisted Russia-based company Volasys Silver Star, China-based China Silver Star and its CEO Jong Song Hwa for violating U.S. sanctions. 

Treasury Secretary Steve Mnuchin said the sanctions were intended to stop the flow of illicit revenue to North Korea from overseas IT workers hiding behind front companies and aliases. The designation blocks any property those targeted may have in the U.S. and prohibits Americans from doing business with them. 

The department said the two information technology companies are actually North Korean-controlled entities. It added China Silver Star had earned millions of dollars from collaborative projects with Chinese and other companies, and Volasys Silver Star, established in early 2017, had earned hundreds of thousands of dollars in under a year. 

The move comes a week after U.S. federal prosecutors charged a North Korean computer programmer over major cyber crimes including the 2014 cyberattack on Sony Pictures Entertainment.