The original Duqu samples were using a C&C server in India, located at an ISP called Webwerks. Since then, another Duqu server has been discovered which was hosted on a server at Combell Group Nv, in Belgium. Overall, we estimate there have been more than a dozen Duqu command and control servers active during the past three years. However, we still do not know who is behind Duqu and Stuxnet, although we have analyzed some of the servers, the attackers have covered their tracks quite effectively.”]
Source: https://securelist.com/the-mystery-of-duqu-part-six-the-command-and-control-servers-36/31863/