Bureau 121 - North Korea's Elite Hacking Group

Not based in North Korea

Not all based in North Korea

Locations for Operations

Bureau 121 training facility is believed to be located in North Korea

Bureau 121 research facility is supposed to be based in North Korea

Bureau 121 operations facility is believed to be located in China, with a separate second command centre based in North Korea (it is a much lower powered facility than the one in China)

Bureau 121 has been looking to migrate a few departments to countries such as Russia & Iran

Bureau 121 would like to have more Points of Presence in a few more countries to gain a larger bandwidth allowance

Sources

BBC News - North Korean hackers 'could kill', warns key defector