Andrey Sabelnikov, of St Petersburg, Russia, has been named in an amended complaint filed by the software giant with the US District Court.
Furthermore, Microsoft alleges that Sabelnikov registered 3,723 "cz.cc" website subdomains, and misused those subdomains to operate and control the Kelihos botnet for the purposes of sending spam.
What is perhaps most surprising is Sabelnikov's background. According to his public LinkedIn profile, from 2005-2007 he was a senior developer and product manager at Agnitum, a Russian security firm well-known for its firewall software.
There is no suggestion that Agnitum are connected with the allegations, or that their security software - which includes anti-virus products - are compromised in any way.
Microsoft, working with the computer security industry, neutralised the Kelihos botnet in September 2011. Despite that Richard Boscovich, senior attorney for Microsoft's Digital Crimes Unit, says that thousands of computers remain infected and that the case "is not over."
A settlement was agreed last year between Microsoft and Dominique Piatti and his company dotFREE Group, which owned cz.cc, giving Microsoft control of the subdomains.
That also had the positive side effect of taking a number of websites offline that had been distributing the MacDefender family of malware which plagued Mac users last year.