North Korea has long been one of the world's leading weapons proliferators, enthusiastically selling its technology to rogue nations for money to prop up its society and finance the development of its weapons systems.
In particular, North Korea has supplied missiles and built missile production facilities for Iran, Syria, Libya, and Egypt. Syria, for example, purchased complete Scuds and production equipment from North Korea, and Pyongyang has been engaged in joint missile development with Egypt for two decades. North Korea is now reportedly offering countries such as Egypt, Iran, Iraq, Libya, Syria, and Yemen a more accurate version of the Scud B missile, which has a range of nearly 300 miles.
Iran is North Korea's principal customer for weapons and technology, and it has been the site of a number of missile tests carried out on North Korea's behalf. North Korea may have sold one of its most sophisticated missiles, the Nodong, which has the capability of carrying nuclear weapons more than 1200 kilometers, to Iran. Meanwhile, the Shahab-3 missile under development in Iran — with a range of 1,300 kilometers — is reportedly based on the Nodong. North Korean experts are also believed to have helped Iran with its centrifuges.
More worrisome even than the missile transfers is the threat of the proliferation of weapons of mass destruction. According to the Defense Department, Pyongyang is currently capable of producing large quantities of nerve, blister, and blood chemical warfare agents. These could be easily transferred to nations or terrorists.
North Korea could export plutonium from its nuclear weapons program, as well as weapon design data, to Iran and other Middle East nations willing to pay for it. In the worst-case scenario, the Koreans move forward with the production of nuclear bombs and then stockpile enough to have a surplus for sale to the highest bidders.
Sources: Michael Eisenstadt, "Iran's Nuclear Program: Gathering Dust or Gaining Steam?", Washington Institute for Near East Policy, (February 3, 2003); Ha'aretz, (February 23, 2003); "The Proliferation Primer," International Security, Proliferation, and Federal Services Subcommittee, United States Senate Committee on Governmental Affairs, A Majority Report, (January 1998)