Just in case nobody has mentioned it already, those NK subs each have a very distinct sonar signature.

If anyone thinks they can get anywhere near our coast without being detected they are drinking their bathwater.

The other thing is that they still are dangerous. NK may not have the capability of launching a ballistic missile from a sub but they could put a nuclear bomb on one or in an electric mini-sub launched from it and wreak havoc that way.

In today's world it is difficult to let a madman be in control of such devices. I will be glad when/IF both Russia and China will wake up and realize their little "NK pet dog" might take a notion to turn and bite them in the ass.