North Korea is responsible for last month's devastating attacks on the network of Sony Pictures Entertainment, the FBI said in a Friday statement The hackers stole terabytes of data from Sony's network and leaked it to journalists, who published embarrassing revelations about the studio. A vague terrorist threat from the hackers caused Sony to shelve The Interview, a comedy about a plot to assassinate North Korean leader Kim Jong Un.

Several factors point to North Korea's involvement

Even before today's announcement from the US government, there were several reasons to suspect that North Korea was responsible for the attacks. Some of the malware used in the attack seems to have been written in the Korean language. The attacks also use tactics similar to those used against targets in South Korea in 2013 and Saudia Arabia in 2012.

The hackers' apparent obsession with The Interview also seems to point toward North Korea.

Now the FBI has added additional evidence.

"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," the agency wrote.

"The FBI also observed significant overlap between the infrastructure used in this attack and other malicious cyber activity that the US government has previously linked directly to North Korea." For example, IP addresses used in the attack were linked to the Hermit Kingdom.