Duqu has been called the spawn of Stuxnet, or maybe some sort of stepchild or second cousin. Initial analysis came from some similarities in the code of the two attack tools. Now that researchers have had more time to pull Duqu apart and see how it works, it seems more and more likely that the two were written by the same group. In the second part of an interview with Costin Raiu, Threatpost editor Dennis Fisher talks with Raiu about the similarities and targets for Duqu and why the authors may have made a key mistake.
Source: https://threatpost.com/how-duqu-authors-may-have-erred-112211/75919/