8.36am: Twitter and Facebook have been hit back at Anonymous, the group behind much of the online mischief making. Charles Arthur has the latest on overnight’s cat and mouse game:

Facebook yesterday acted against the group by closing down its Facebook page.

Not long afterwards Twitter suspended the “Anon_Operation” account immediately after it tweeted a link apparently to hacked MasterCard numbers which were being posted to the code site Pastebin.com.

The account had around 22,000 followers at the time. But it rapidly reappeared under a new name, Anon_Operationn, offering links to the Internet Relay Chat servers where the members of the Anonymous group have been planning online attacks against sites and organisations deemed to be antagonistic to Wikileaks.

7.52am: MasterCard, Visa, the Swedish prosecution authority, Joe Lieberman, Sarah Palin, PayPal, Twitter, PostFinance, Amazon and EveryDNS.net. It is an very eclectic mix, but their websites are all under attack, or threat of attack, by supporters of WikiLeaks.The Daily Mail is alarmed. ”WIKILEAS: NOW IT’S CYBER WAR”, shouts its front page.

More sober analysis is available elsewhere. The New York Times says the WikiLeaks storm poses an awkward dilemma for Facebook and Twitter.

Both Facebook and Twitter — but particularly Twitter — have received praise in recent years as outlets for free speech. Governments trying to control the flow of information have found it difficult to block people from voicing their concerns or setting up meetings through the sites.

At the same time, both Facebook and Twitter have corporate aspirations that hinge on their ability to serve as ad platforms for other companies. This leaves them with tough public relations and business decisions around how they should handle situations as politically charged as the WikiLeaks developments.

Activists from Anonymous, the group behind Operation Payback, talk to the Economist in a revealing blogpost.

The reporter chatted online with the group as they appeared to be discussing whether or not to target the Metropolitan Police for arresting the founder of WikiLeaks Julian Assange. They decided against.

Anons do understand their limitations. The ones I talked to know that to take down a Swedish prosecutor’s website does not halt the prosecution in Sweden. They described their motivations, variously, as trying “to raise awareness”, “to show the prosecutor that we have the ability to act” and “damage and attention”. This is all that a denial-of-service attack can do: register protest. It is not cyberwar. It is a propaganda coup.

The two women whose complaints of sexual assault triggered Julian Assange’s arrest have also been targeted in vicious online campaign, according to their lawyer.