WASHINGTON -- Police in Ukraine raided an apartment and arrested a man believed to be connected to the cyber theft ring that investigators have dubbed “The Avalanche Network.”

Authorities say the network had computer servers in at least four countries and stole hundreds of millions of dollars.

Acting U.S. Attorney Soo Song CBS News

“We’ve successfully identified 250,000 infected computers in 189 different countries throughout the world,” said Soo Song, the acting U.S. attorney for the western district of Pennsylvania.

“We calculate that 20,000 of those malware-infected computers are here in the United States,” Song said.

In Allegheny County, Pennsylvania, investigators accuse the cyber thieves of taking over and “freezing” some government computers until a ransom was paid.

And criminals hacked two unnamed Pennsylvania companies and attempted wire transfers totaling more than $600,000.

The thefts used so-called Goznym malware, which infects computers after victims click on a phony link.

Investigators say those behind Avalanche were providing servers for other other criminals to use in cyberattacks. Often stolen money was then laundered through “money mules” -- unsuspecting people who were tricked into participating.

The big break in the operation came when German police reverse-engineered the code that Operation Avalanche was using. The investigators then brought in the FBI to help trace the servers, some of which were in the U.S. and Canada.