Whether North Korea is ultimately responsible for the breach of Sony's computers remains to be seen, but what is certain is that the country has some of the best hackers in the world.
Jang Se-yul, who has escaped to South Korea since 2007, explains how hackers are trained.
He claims that Mirim University is where most North Korean hackers come from. The program they attend is very demanding, and out of 5,000 applications each year, about 100 students are accepted.
They attend six 90-minute classes each day and learn various languages such as C.
They are concerned with decrypting Microsoft, such as the Windows operating system, and how to attack technological systems of rival countries, such as the United States and South Korea.
But the main thing they learn is how to develop hacking programs that don't rely on existing systems.
Jang Se-yul claims that the level of North Korean hackers is as high as that of Google or the CIA programmers, if not even better.
Once they take up the position, they spend two years in the country they have been assigned to, learning its language and culture.
In fact, the ability to travel abroad and the fact that they are paid in American dollars is one of the reasons so many try to do this job.
Jang Se-yul estimates that Bureau 121 employs around 1,800 cyber warriors.
Furthermore, their living conditions are much better than those of their other compatriots, they earn more money, have a free apartment in the center of the capital, Pyongyang, and have many privileges, such as access to the internet.
They are among the 1% of people who are happy with their lives in North Korea.
Knowing what is going on in the outside world, thanks to access to the internet, one could bribe them, but the truth, according to Jang Se-yul, is that it is impossible to convince them to leave their country.
As he claims, North Korea's purpose is to have a weapon against countries that are economically and militarily superior.
He adds that he is certain that North Korea is behind the attacks on Sony and concludes by saying that the US should take them seriously.
