The FBI has seized control of 15 websites that let people pay to knock individuals and other sites offline.
The so-called booters sought to swamp targets with huge amounts of data in what are known as distributed-denial-of-service (DDoS) attacks.
Three US men have been charged with allegedly offering DDoS services.
“DDoS-for-hire services such as these pose a significant national threat,” US Attorney for Alaska Bryan Schroder said in a statement.
The FBI says more than 200,000 attacks have been launched via just one booter site.
The Department of Justice said David Bukoski, from Alaska, and Matthew Gatrel and Juan Martinez, from California, had been charged in connection with the booter services,