In a rather startling development (for the South Korean Navy) North Korea recently released video showing its warships firing what appears to be a Russian Kh-35 anti-ship missile. This is a new missile, having entered Russian service in 2003 although it was being offered for export in the late 1990s (when the Russian Navy could not afford to.)
Russia denies it sold the missiles to North Korea thus the only other likely source is Burma, which has been conducting an illegal (and always denied) arms trade with North Korea for over a decade. Other export customers have been Algeria, India, Venezuela and Vietnam.
The Kh-35 anti-ship missile is similar to the American Harpoon but lighter (520 kg/1,150 pounds, compared to 728 kg) and has less range (130 kilometers compared to 224 for the latest version of Harpoon). The Kh-35 (also known as the SS-N-25 or Switchblade) can also be fired from helicopters, aircraft or shore batteries. The Kh-35 has not been used in combat yet but it appears to be a competent Harpoon-type weapon.
The problem for South Korea is that they have equipped their warships with defenses to defeat older type anti-ship missiles the North Koreans have been using for years. South Korea will have to upgrade the training and some of the defense equipment to deal with the Kh-35. At this point South Korean and American intelligence are trying to find out how many Kh-35s North Korea has and where they came from. Fortunately North Korea has few ships that can carry the Kh-35.