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More cyber attacks in retaliation for attempts to block the WikiLeaks website are likely in a "data war" to protect Internet freedom, a representative of one of the groups involved said on Thursday.

Though no major websites appeared to be under
attack early on Thursday, Swedish newspaper Aftonbladet said the Swedish
government’s website was down for a short time during the night. Sweden
had issued an arrest warrant for WikiLeaks’ founder.

has targeted mainly companies which have decided for whatever reason
not to deal with WikiLeaks. Some of the main targets involve Amazon,
MasterCard, Visa and PayPal," a spokesman calling himself "Coldblood"
told BBC Radio 4.

"The campaign is
not over from what I’ve seen, it’s still going strong. More people are
joining, more and more people are downloading the voluntary botnet tool
which allows people to command dos (distributed denial of service)
attacks," he added.

The speaker, who had an English accent, said he was aged 22 and was a software engineer.

card giants MasterCard and Visa came under intense cyber attack on
Wednesday as supporters of WikiLeaks retaliated for moves against
WikiLeaks founder Julian Assange after the release of U.S. diplomatic
cables that angered and embarrassed the Obama administration.

see this as becoming a war, but not your conventional war. This is a
war of data. We are trying to keep the Internet free and open for
everyone, just the way the Internet always has been," "Coldblood" added.

is in a London jail after he was arrested over allegations of sexual
assault in Sweden. His supporters say the accusations against him are
politically motivated.

"It’s very
hard to get hold of anyone from WikiLeaks. The only (person) you could
really get hold of was Julian, but unfortunately he’s not available at
the moment," said "Coldblood".

(Reporting by Keith Weir with additional reporting by Patrick Lannin in Stockhol; editing by Mark Heinrich)