Spam-fighting organization Spamhaus, with offices in London and Geneva, works with email providers around the globe to block spam from entering inboxes.
It has been in a battle in the last week with Dutch website hosting company Cyberbunker after adding it to its spam "blacklist," CNET reported Wednesday.
Cyberbunker has based its business on a willingness to accept any and all customers, turning away only those engaged in child pornography and terrorism-related activities, CNET said.
A massive distributed denial of service attack was launched against Spamhaus March 19, a spokesman for the anti-spam group told The New York Times in a statement Wednesday.
For the past week, Spamhaus has been hit with attacks peaking at 300 gigabits per second, many times greater than similar attacks that have in the past targeted sites with powerful defenses such as banks.
The sheer amount of data hitting the Internet's Domain Name System because of the attack on Spamhaus has resulted in some slowdowns across the Internet, CNET reported.
Cyberbunker has not confirmed it's behind the attacks and has not responded to requests for comment, CNET said.