Big difference between this and missiles: with missiles you have to pay extra per shot. With this, you release one into the wild and from then the marginal cost

Big difference between this and missiles: with missiles you have to pay extra per shot. With this, you release one into the wild and from then the marginal cost to send out more copies is orders of magnitude lower than the original development cost. As for "mutations and clones" - these are computer viruses, not the organic kind. People can imitate the techniques and develop on them, but as long as copies from and to USB drives maintain their multiple-9s accuracy there won't be much spontaneous change outside of the deployer's control. Instead, the big uncertainty factor with worms and viruses has usually been emergent behavior when the infected computers network into one very large system, leading to behaviors that don't show up in small-scale tests. The way it's described, Stuxnet is inherently limited both by its transmission method - USB sticks - and by its target systems - large embedded systems, typically not network-connected, and with a very standard configuration provided from Siemens.