That is what the AMD-CELL anti-ballistic missiles system is for.Without US protection/DPRK involved(presumably, I know it is quite unrealistical), ROK can't even stand a round of SRBM attack.
The ROK is not buying the SM-3 or PAC-3. Instead, KM-SAM-ER will enter production by 2016 to fill the gap until the KL-SAM becomes ready in 2020. KM-SAM-ER is an upgraded version of KM-SAM with the flight ceiling doubled to 40 km and the speed increased to Mach 8, enough to engage Scuds.though SM-3 and Aegis is good, thoese systems stand no chance in front of thousands of SRBMs(moreover, without US involved, where do you get data?)