The gang, known as Cl0p, has hacked a number of American targets, including the University of Miami, Florida, Stanford University, University of Maryland, and the University of Colorado, demanding payment to either keep their systems functional or to not publish material they were able to steal.

Ukraine's announcement coincided with President Joe Biden's meeting with Russian President Vladimir Putin in Geneva. Biden pressed Putin to take action against ransomware hackers who operate with impunity within Russia's borders.

Ransomware has become a significant problem in the United States. Recent ransomware attacks tiggered the Colonial Pipeline, shutting down the country's largest fuel pipeline for five days, and JBS, one of the country's largest meat suppliers.

The prolific ransomware gangs are believed to operate in Eastern Europe and Russia in particular.

Ukraine's cyber police announced they had arrested six people involved with Cl0p and seized a number of computers, cars and about five million Ukrainian hryvnias ($185,000) in cash.