While there is insufficient evidence to prove that North Korea is pursuing countermeasures or penetration aids (penaids), the lack of evidence certainly does not prove that they are not. The technology behind producing penaids — or still more dangerous — multiple independent reentry vehicles (MIRVs) is difficult, but not more difficult than what North Korea has already accomplished.
Not only does much of the technology date back decades, but North Korea has already proven that it can use cutting-edge design, modeling, and testing practices as seen in their nuclear and missile programs to date. Since every state that preceded them has investigated countermeasures, it is likely that North Korea is as well. In the near term, it is likely that North Korea will pursue simple decoys, which are light and relatively cheap. However, in the long-term North Korea will continue to miniaturize warheads in order to place multiple nuclear warheads on a single intercontinental ballistic missile capable of striking the US mainland.
A conservative estimate of the Hwasong-15 suggests that in the future it could hold 3-4 reentry vehicles of approximately 500-750kg each. To achieve this, North Korea would need to continue to miniaturize its warheads, design a propulsion system for the bus, and master the complex mathematics of guiding multiple reentry vehicles.