Federal investigators took down one of the world’s largest malicious botnets, one that helped generate tens of thousands of fraudulent transactions that cost victims billions — including many related to COVID relief funding.

Law enforcement also arrested the botnet’s administrator, YunHe Wang, a Chinese national. He’s been accused of orchestrating an international plot to deploy malware and surreptitiously sell access to the infected computers’ IP addresses. IP addresses, a string of numbers and dots, act as unique identifiers for the devices and domains on the internet, allowing them to communicate with each other and send information back and forth.

Wang is charged with leading an operation — known as the 911 S5 Botnet — that deployed 19 million compromised IP addresses in over 190 countries, using them as “an infrastructure highway for carrying out crimes such as bomb threats, financial fraud, identity theft, child exploitation, initial access brokering, and many other computer crimes,” according to FBI cyber division deputy assistant director Brett Leatherman.

Officials confirmed Wang was financially motivated, with no known direct ties to nation-states.