How nations risk nuclear terrorism

(CNN) -- World leaders are meeting in Seoul this week to discuss how to deal with the threat of nuclear terrorism.

The effort to prevent the misuse of nuclear materials and the spread of nuclear weapons has long-placed most emphasis on defensive measures. These are essentially on the "supply side" -- aiming to choke off the flow of nuclear weapon components and radiological materials to terrorists. While there is a place for such steps, there is another, and perhaps more successful way, to accomplish the goal.

One of the gravest threats to nuclear proliferation arises from the nations that use proxy groups -- seemingly independent organizations that are paid to further the interests of governments. Read More