A Twitter user known as @ibomhacktivist claimed responsibility for the cyberattack, saying it was executed in response to MasterCard’s decision to terminate credit card processing by donors for the whistle-blower site WikiLeaks last November 2010.
"MasterCard.com DOWN!!!, thats what you get when you mess with @wikileaks @Anon_Central and the enter community of lulz loving individuals :D," read the @ibomhacktivist Tweet.
MasterCard confirmed the attack in a statement although stopped short of calling the outage a “denial of service attack.”
“We can confirm that MasterCard's corporate, public-facing Web site experienced intermittent service disruption, due to a telecommunications/Internet Service Provider outage that impacted multiple users. It is important to note that no cardholder data has been impacted and that cardholders can continue to use their cards securely. We are continuing to monitor the situation closely.”
The hack come more than half a year after global hacker collective Anonymous launched a spate of denial of service attacks in 2010 against several payment card companies, including MasterCard, Visa, PayPal and the Swiss Bank PostFinance. Anonymous claimed that the retaliatory cyberattacks targeted the payment processing companies for ending service agreements with the whistle-blower site shortly after WikiLeaks published parts of 250,000 classified diplomatic cables.
Denial of service attacks occur by overwhelming a network with more requests than it can handle, causing the system to choke and crash.
Meanwhile, Anonymous seems to be picking up where notorious hacker group LulzSec left off. After a 50-day hacking spree, LulzSec formally passed the torch to hacker group Anonymous over the weekend, maintaining that the global hacker collective would take over all responsibilities of Operation Anti-Security with cyberattacks against high-profile governments and organizations. The six-member LulzSec is likely being absorbed into the larger hacker group, Anonymous members said.
"We like to clarify again: All LulzSec members are accounted for, nobody is hiding. Only a name was abandoned for the greater glory #AntiSec," Anonymous said in a Twitter post .
Over the past seven weeks, LulzSec emerged from relative obscurity to center stage with a series of high-profile attacks against the Web sites of the CIA, the U.S. Senate , SonyPictures.com , and the Arizona Department of Public Safety .
Before it shuttered operations, LulzSec published copious data gleaned from its most recent attacks against AOL, AT&T, online game Battlefield Heroes, the FBI, the NATO bookstore and the Navy.
Anonymous wasted no time in picking up where LulzSec left off by releasing a 625-MB file containing sensitive documents as well as hacking and counter-hacking information Monday, coupled with a link to the CDI Sentinel program page , which offers free cybersecurity training, among other things.
The LulzSec/Anonymous merger also reportedly appears to be continuing its hacking campaign with attacks against the Tunisian government, apparently in protest of its Internet censorship practices.