Bureau 121

Bureau 121 is a North Korean cyberwarfare agency, which is part of the General Bureau of Reconnaissance of North Korea's military. According to American authorities, the General Bureau of Reconnaissance (also termed Reconnaissance General Bureau) manages clandestine operations and has six bureaus. Cyber operations are thought to be a cost-effective way for North Korea to maintain an asymmetric military option, as well as a means to gather intelligence; its primary intelligence targets are South Korea, Japan, and the United States. Bureau 121 was created in 1998.

Another known cyberwarfare unit in the General Bureau of Reconnaissance is called No. 91 Office.

Staffing
According to a report by Reuters, Bureau 121 is staffed by some of North Korea's most talented computer experts and is run by the Korean military. A defector indicated that the agency has about 1,800 specialists. Many of the bureau's hackers are hand-picked graduates of the University of Automation, Pyongyang. While these specialists are scattered around the world, their families benefit from special privileges at home.

Targets and methods
The activities of the agency came to public attention in December 2014 when Sony Pictures canceled the opening of its movie The Interview after its computers had been hacked. Bureau 121 has been blamed for the cyber breach, but North Korea has rejected this accusation.

Much of the agency's activity has been directed at South Korea. Prior to the attack at Sony, North Korea was said to have attacked more than 30,000 PCs in South Korea affecting banks and broadcasting companies as well as the website of South Korean President Park Geun-Hye North Korea has also been thought to have been responsible for infecting thousands of South Korean smartphones in 2013 with a malicious gaming application. The attacks on South Korea were allegedly conducted by a group then called DarkSeoul Gang and estimated by the computer security company Symantec to have only 10 to 50 members with a "unique" ability to infiltrate websites.

American authorities believe that North Korea has military offensive cyber operations capability and may have been responsible for malicious cyber activity since 2009. As part of its sophisticated set-up, cells from Bureau 121 are believed to be operating around the world. One of the suspected locations of a Bureau 121 cell is the Chilbosan Hotel in Shenyang, China.