Since North Korea bombarded the South Korean island of Yeonpyeong last month, details of the military responses have been leaking out. North Korea was noticed using their anti-aircraft radars, especially for their missiles, right after the bombardment on November 22nd. The electronic beams used to guide the elderly North Korean anti-aircraft missiles could be detected all along the western portion of the border. The North Koreans also used some of their jammers to shut down South Korean attempts to use UAVs to scout the DMZ. Manned recon aircraft and satellites showed that the North Korean moved more anti-aircraft missiles and Silkworm anti-ship missiles to the west coast near the DMZ during, and after, the bombardment.
Most of the anti-aircraft missiles are either made in North Korea, or imported from China. North Korea has a lot of the Chinese versions (the HQ-2) of the Russian SA-2 systems. This is a system developed in the 1950s. The Chinese have upgraded the SA-2 with modern electronics, an improved warhead, better rocket motors and more maneuverability. But the North Koreans have many older models still in service, and many of these are probably of uncertain reliability. American electronic countermeasures can probably defeat all models of the HQ-2 and SA-2. Newer models of the HQ-2 have a range of 40 kilometers, and will hit the target 70 percent of the time (if there are no countermeasures.) The HQ-2 radars have a hard time dealing with stealthy aircraft, and the radar is needed to guide the missile to its target (via radio signals from the ground to the missile).
The Silkworm anti-ship missiles are Chinese, based on a 1950s Russian design. The two ton Silkworm didn't enter service until the 1980s, and is still found in the arsenals of nations who can't afford the more modern stuff. The Silkworm looks like a small jet fighter, without a cockpit. It has a range of about 90 kilometers and is effective against warships that have not turned on their defenses.