North Korea is the new age pirate and they are not after gold but they are after bitcoin. According to this article North Korea has successfully hacked bitcoin into their hands starting 2013 to 2015. It was also estimated that they have harvested 100 million yuan worth of bitcoin every month from hacking. The community must not be silent against it rather there must be some measures to be done so to avoid this unwanted hacking incidents.
Well it seems like that whatever the North Koreans do, it is always somehow related to hacking , lol.
I think that it does sound likely it is something that the North Koreans would do, as they have forged notes before as well of the United States actually.
This shouldn't be a worry to anyone here though, because the internet in North korea is so bad anyways they can't brute force anything
All jokes aside, as long as you secure your wallet, preferably even with BIP38 encryption, you should be fine.
I wouldn't be surprised if majority of these coins stolen are actually from web wallet services, like Coinbase.
It is easier to hack a email and reset the password, than to crack a private key with brute force.
Stay safe !