Dozens of domain names linked to some of the world's leading distributed denial-of-service sites have been seized by the U.S. Several of the seized sites are still online, according to a report.

The U.S. Department of Justice announced in a press release on Wednesday that it had taken down 48 domain names associated with some of the world's most popular booter platforms. These services, often marketed as sites for bandwidth stress-testing networks, allow low- skilled individuals to carry out distributed denial of service attacks designed to overwhelm websites and networks.

The U.K.'s National Crime Agency, Dutch police, and Europol worked together to carry out the takedowns.

The DOJ said these booter sites were involved in attacks against a wide array of victims in the U.S. and abroad. More than 30 million attacks have been carried out by a site seized by Europol.

While many of the websites targeted by the operation now display a message stating that they have been seized by the FBI, at least eight of the sites supposedly seized by U.S. prosecutors continue to load as normal, according to a new report. It's not clear why these sites are still loading.

One of the DDoS booter sites allegedly seized by the DOJ, but which remains active and operational.

The DOJ is said to have seized one of the booter sites. The image is from TechCrunch

Law enforcement officials arrested seven people who were allegedly in charge of the hacker services. Criminal charges have been filed against six people in the United States.

The service run by Laing is still online.

The FBI splash-pages were delayed, according to a DOJ spokesman. The registry is working with us to make this happen. The websites are no longer functioning and can't be used to launch attacks.

The NCA arrested an 18-year-old man in the UK who is suspected of being an administrator of one of the seized sites. Customer data from all of the booter sites will be analyzed by law enforcement, according to the NCA.

The NCA warned that admins and users based in the UK would be visited by police in the coming months.

The comments from the Justice Department have been updated.

FBI kicks some of the worst ‘DDoS for hire’ sites off the internet