Two men from Lanarkshire, in Scotland, were arrested, while an address in Bradford, West Yorkshire - linked to attacks on seven of the UK’s biggest banks last year - was searched.
Other arrests were made in Serbia, the Netherlands, Croatia and Hong Kong, while servers were seized in Germany as the service was shut down on Wednesday.
Europol said the website was considered the world’s biggest seller of so-called distributed denial of service (DDOS) attacks, in which high volumes of internet traffic are launched at target computers to disable them.
Investigators said cybercriminals used the website, which could be rented for as little as 14.99 US dollars (£10.70), to launch more than four million attacks around the globe.
It had more than 136,000 registered users and could be rented by people with little or no technical knowledge to cripple online services offered by government institutions, police forces and banks.
The National Crime Agency (NCA), which led the international probe, said its officers identified a “criminal infrastructure” in the Netherlands as part of an ongoing campaign against ‘DDOS-for-hire’ services.
Jo Goodall, a senior investigating officer on the force, said: “A significant criminal website has been shut down and the sophisticated crime group behind it stopped as a result of an international investigation involving law enforcement agencies from 11 countries.
“Cybercrime, by default, is a threat that crosses borders and our response must be one that utilises the close international law enforcement collaboration that is crucial to tackling this threat.
“The arrests made over the past two days show that the internet does not provide bullet-proof anonymity to offenders and we expect to identify further suspects linked to the site in the coming weeks and months as we examine the evidence we have gathered.”
Gert Ras, from the Dutch National Police, said: “By taking down the world’s largest illegal DDOS seller in a worldwide joint law enforcement operation based on NCA intelligence, we have made an unprecedented impact on DDOS cybercrime.
“Not only were the administrators of this illegal service arrested, but also users will now face prosecution and civil liability for caused damage.”