本周三，万事达卡、visa信用卡、瑞士银行以及前美国副总统候选人佩林等组织和个人的网站遭到黑客攻击，一个叫做“匿名”的黑客志愿者团体声称对此次行动负责，并表示受到攻击的组织和个人都曾经有过对维基解密网站及其创始人阿桑奇不利的行为和言论。

Hackers¹ rushed to the defense² of WikiLeaks on Wednesday, launching attacks on MasterCard, Visa, Swedish prosecutors³, a Swiss bank, Sarah Palin and others who have acted against the site and its jailed founder⁴ Julian Assange.

Internet "hacktivists" operating under the label "Operation Payback" claimed responsibility in a Twitter message for causing severe technological⁵ problems at the website for MasterCard, which pulled the plug on its relationship with WikiLeaks a day ago.

MasterCard acknowledged "a service disruption" involving its Secure Code system for verifying（核查） online payments, but spokesman James Issokson said consumers could still use their credit cards for secure transactions. Later Wednesday, Visa's website was inaccessible⁷.

The online attacks are part of a wave of support for WikiLeaks that is sweeping⁸ the Internet. Twitter was choked with messages of solidarity⁹（团结） for the group, while the site's Facebook page hit 1 million fans.

Late Wednesday, Operation Payback itself appeared to run into problems, as many of its sites went down. It was unclear who was behind the counterattack.

MasterCard is the latest in a string of U.S.-based Internet companies — including Visa, Amazon.com, PayPal Inc. and EveryDNS — to cut ties to WikiLeaks in recent days amid intense U.S. government pressure. PayPal was not having problems Wednesday but the company said it faced "a dedicated¹⁰ denial-of-service attack" on Monday.

Meanwhile, a website tied to former Republican vice⁶ presidential candidate Sarah Palin came under cyberattack, she said. In a posting on the social networking site Facebook last week, Palin called Assange "an anti-American operative（侦探，技工） with blood on his hands." An aide said staff moved quickly to secure the website and no data was compromised.

The pro-WikiLeaks vengeance¹¹ campaign on Wednesday appeared to be taking the form of denial-of-service attacks in which computers are harnessed — sometimes surreptitiously（偷偷地，秘密地） — to jam target sites with mountains of requests for data, knocking them out of commission.

Per Hellqvist, a security specialist with the firm Symantec, said a network of web activists¹² called Anonymous¹³ — to which Operation Payback is affiliated¹⁴（隶属，加入） — appeared to be behind many of the attacks. The group, which has previously¹⁵ focused on the Church of Scientology and the music industry, is knocking offline websites seen as hostile to WikiLeaks.