Pyotr Levashov was arrested in Barcelona at the end of last week on a US computer crimes warrant, a spokeswoman for Spain's National Court, who spoke on condition of anonymity in line with court rules, told the Associated Press.

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According to the cybersecurity site KrebsOnSecurity, Levashov was allegedly responsible for "running multiple criminal operations tha tpaid virus writers and spammers to install 'fake antivirus' software" under the alias "Severa."

The site adds: "There is ample evidence that Severa is the cybercriminal behind the Waledac spam botnet, a spam engine that for several years infected between 70,000 and 90,000 computers and was capable of sending approximately 1.5 billion spam messages a day."