South Korea is buying the American AAR-47 Missile Approach Warning System (MAWS) for some of its AH-1S helicopter gunships. This purchase consists of sixty sensors, to detect approaching missiles, plus computer equipment to make the decision to alert the crew and release flares (the most typical countermeasure, which lures the heat seeking missile away from the aircraft). Some nations use a more expensive laser based countermeasures system, where the laser "blinds" the oncoming missile with laser light.
The AAR-47 first became available in 1998 and was only able to warn against approaching missiles. Since then there have been several upgrades. The model South Korea is buying is quite recent and also warns of incoming gunfire and RPG grenades. There are add-on modules that will also warn of lasers hitting the aircraft. Over 5,000 AAR-47 systems have been delivered so far. In addition thousands of older AAR-47 systems have had their components (especially the four sensors per system) upgraded so far.