After weeks of speculation the FBI has taken the dramatic step of officially linking North Korea to the cyber attack carried out on Sony Pictures late in November.

The FBI statement to the press says: "The FBI now has enough information to conclude that the North Korean government is responsible for these actions [the Sony attack]."

The agency cites three reasons that have led them to this conclusion:

• "Technical analysis of the data deletion malware used in this attack revealed links to other malware that the FBI knows North Korean actors previously developed. For example, there were similarities in specific lines of code, encryption algorithms, data deletion methods, and compromised networks."
• "The FBI also observed significant overlap between the infrastructure used in this attack and other malicious cyber activity the U.S. government has previously linked directly to North Korea. For example, the FBI discovered that several Internet protocol (IP) addresses associated with known North Korean infrastructure communicated with IP addresses that were hardcoded into the data deletion malware used in this attack."
• "Separately, the tools used in the SPE attack have similarities to a cyber attack in March of last year against South Korean banks and media outlets, which was carried out by North Korea."

The FBI says that the, "destructive nature of this attack," poses a threat to US companies, ordinary citizens, and the federal government.

It added: "North Korea’s actions were intended to inflict significant harm on a US business and suppress the right of American citizens to express themselves. Such acts of intimidation fall outside the bounds of acceptable state behavior. The FBI takes seriously any attempt—whether through cyber-enabled means, threats of violence, or otherwise—to undermine the economic and social prosperity of our citizens."

Sony announced on Wednesday that it was abandoning plans to release The Interview.

North Korean officials have previously refuted claims that they were behind the attack - but they did endorse it as a "righteous deed."

It is unclear what action the US will now take.