Mastercard’s website was down for several hours this morning, and now it appears as though Visa’s is offline as well, as these sites have become the targets of ongoing DDoS attacks.

And so the infowar rages on today with these latest shots apparently fired by Anonymous, a vigilante group of hacktivists loosely affiliated with the message board 4chan. Anonymous has been fighting an ongoing crusade dubbed Operation Payback for the last several months. Using distributed denial of services attacks, this group has managed to knock off-line a number of pro-copyright websites, belonging to the likes of the U.S. Trademark Office and musician Gene Simmons.

But following the latest series of events surrounding the Wikileaks saga, Anonymous has offered its resources in the service of “payback” against some of the companies that have recently blocked WikiLeaks’ financial resources. PayPal was offline briefly on Monday, as was the website for the Swiss bank that recently froze Julian Assange’s assets there. Today, Mastercard and Visa, both of which have announced that they will block donations to WikiLeaks, were the target.

“While we don’t have much of an affiliation with WikiLeaks,” a statement on the Anonymous website reads, “we fight for the same reasons. We want transparency and we counter censorship. The attempts to silence WikiLeaks are long strides closer to a world where we can not say what we think and are unable to express our opinions and ideas.”

Certainly taking out your political opposition’s websites hardly makes you look like the most ardent defender of all free speech, only some of it. But in further twists in this story of finances, censorship, and free expression, it appears that Datacell, an Icelandic IT company that was processing payments for WikiLeaks’ donations now says it is investigating legal actions it can take since the credit card companies have interfered with its rights to do business.

Stay tuned, as this battle seems far from over.