It was previously thought the site had been knocked offline after being hit by a distributed denial-of-service (DDoS) attack. MasterCard s contentious relationship with WikiLeaks began in December, 2010, when they, along with PayPal and Visa, agreed to stop processing donations to the group following their leak of more than 250,000 U.S. diplomatic cables. Wikileaks claimed hacktivists took down the site in protest over the continuing illegal WikiLeaks fiscal embargo and confirmed that VISA, PayPal, Bank of America and Western Union.
Source: https://threatpost.com/isp-outage-not-hackers-take-down-mastercards-site-062811/75375/