Spamhaus says that the “distributed denial of service” (DDoS) attacks on its computer servers has subsided. The cyber-attacks during mid-week crippled the Internet for many users.

It is still unknown who perpetrated the attack, but the unknown attackers were apparently unhappy with the British company’s efforts to block spam email. Thousands of computers that had been infected with a computer virus to become part of what is known as a “botnet,” which then was used to send huge amounts of data to targeted servers in an effort to overwhelm them, attacking one link in the Internet infrastructure and slowing down other parts of the Internet as well.