On Tuesday, international law enforcement officials took down a ring of cybercriminals responsible for over 4 million DDoS attacks.

A joint operation between the United Kingdom’s National Crime Agency, Dutch police, and Europol shut down the website WebStresser and arrested six of its administrators. The enforcement action also received the cooperation of more than a dozen other agencies in seizing assets and infrastructure items in Scotland, Croatia, Canada, Serbia, Germany, Australia, Italy, Spain, Hong Kong, and the United States.

According to the seizure notice on the website, the action was part of a campaign called Operation Power OFF.

“The domain name Webstresser.org has been seized by the United States Department of Defense, Defense Criminal Investigative Service, Cyber Field Office in accordance with a warrant issued by the United States District Court for the Eastern District of Virginia. This domain name has been seized in conjunction with Operation Power OFF.

The operation is aimed at the takedown of the illegal DDoS-for-hire-service [Webstresser].”

The Hacker News reports the website had over 136,000 users that could order a DDoS attack on any target for about 10 British pounds. The fee could also be paid in cryptocurrency, and the “customer” needn’t have any technical or hacking knowledge.

“Any registered user could pay a nominal fee using online payment systems or cryptocurrencies to rent out the use of stressers and booters,” said a Europol spokesperson.

The site was also linked with seven attacks in the UK last November against government agencies, banks, and the gaming industry.

The names of those who were arrested have not been released.

Gert Ras, head of the Dutch police’s High Tech Crime unit said that the actions resulting from the operation should serve as a warning to users of services such as those provided by WebStresser.

“Don’t do it,” said Ras. “By tracking down the DDoS service you use, we strip you of your anonymity, hand you a criminal record and put your victims in a position to claim back damages from you.”