One thing about North Korea we don't have fret over is their merchant marine fleet being used for terrorism. That's because, for over a decade, the 240 or so North Korean ships have been closely watched. Very closely.
With over 50,000 ocean going vessels out there, that could make it to North America, the U.S. Navy and Coast Guard were forced to develop techniques to deal with the situation. First, only a few thousand ocean going ships regularly visit North America. Most are huge cargo vessels or tankers, constantly moving back and forth between East Asian or Persian Gulf ports and North American destinations. These are easy to watch. So the navy has established a class of ships that get special attention. These are called vessels of interest (VOI). Some get included in this list because they carry hazardous materials (explosives or very dangerous chemicals). Others are VOIs because they are where they shouldn't be, or are simply suspected of involvement in one seagoing criminal activity or another. If a Chinese or African coastal freighter is spotted approaching North America, it becomes a VOI. If a sailor jumps ship in the United States, that vessel becomes a VOI (because this is now considered a method for smuggling terrorists into the country.) More attention is paid to theft at container ports. Its long been common for criminals to smuggle goods (usually drugs) and people (often prostitutes, or just illegal migrants) in via shipping containers. But terrorists could also come in that way. Appeals to port workers patriotism usually provides a steady supply of tips on which crooks are, or might be, crossing the line from thieving to terrorism.
The search for VOIs has also uncovered a lot more nefarious activity on the high seas than the navy had previously suspected. While it was known that North Korea had been shipping illegal goods (drugs, counterfeit cash, weapons) around on its merchant ships, the VOI search uncovered much, much more. The North Koreans have been more active in gunrunning and smuggling illegal raw materials (ore, oil and lumber) out of Africa and Asian hot spots. A recent example came to light last year. On October 30th, a North Koreas merchant ship, the Dai Hong Dan, was boarded by pirates off the coast of Somalia. The North Koreans managed to get off a distress message. The ship was in international waters, 108 kilometers off the coast, unloading sugar to smaller boats. This offshore unloading arrangement was supposed to protect the North Koreans from pirates, or the numerous bandits and warlords on shore. The pirates were actually armed guards hired to protect the crew from real pirates during this unloading operation.
An American destroyer, the USS James E. Williams, was nearby, and rushed to the scene. When the U.S. warship got there, they demanded that the pirates surrender. Meanwhile, on the ship, part of the North Korean crew had managed to barricade themselves in the engine room, where they controlled the speed and direction the ship could move in. But the seven pirates had taken control of the bridge, and refused to surrender. Seeing this, most of the 43 man North Korean crew stormed the bridge, killing two of the seven pirates. Three crew members were badly wounded, and the destroyer captain, using a Korean-American sailor as a translator, offered to treat them. The North Korean captain agreed, and the destroyers helicopter was sent to get the wounded men. American sailors came aboard, applied first aid, and the three wounded North Koreans were transferred to the destroyer for treatment.
So far, there's been no proof that the North Korean smuggling fleet has been servicing terrorist organization. But it's believed the North Koreans would, if the price was right, and the chances of getting caught seemed minimal. Certainly, moving goods in and out of Somalia is one of the most dangerous activities a merchant ship could be involved in. Most of the North Korean ships are old and decrepit. These ships are rather small and slow, and have to scramble for any kind of cargo. So they have a reputation for going anywhere, to carry just about any cargo, if the price is right. The North Koreans are also aware of the U.S. scrutiny, and have a sense that they will be left alone as long as they do not cross the line (deal with terrorists.)
Meanwhile, all VOIs have become a seagoing version of the usual suspects. The same ships keep showing up again and again when the navy, coast guard or port authorities go looking for bad behavior.