NK also is deeply involved in all sorts of "dark web" trade - drugs of all sorts, arms dealing, financial scams etc
And of course they can devote as much of their GDP to arms as they like - its not the weasel like 1% of some European countries. In the past people have spent over 20% of GDP on arms (I seem to remember Israel was one of them). When you think that a Labour Govt in the UK financed an atomic bomb programme straight after the war when times were VERY tough you can see what can be done if it becomes an overriding national priority. And there is so much information out there for free these days - pictures, stories, brochures, books ,,,...... and people who are willing to help anyone for cash as well