BOSTON — A global epidemic of digital extortion known as ransomware is crippling governments, hospitals, school districts and businesses by scrambling their data files until they pay up. Law enforcement agencies have been largely powerless to stop it.

One big reason: Ransomware rackets are dominated by Russian-speaking cybercriminals who are shielded — and sometimes employed — by Russian intelligence agencies, according to security researchers, U.S. law enforcement officials, and now the Biden administration.