The FBI says in a statement that North Korea hacked Sony Pictures; U.S. officials leaked word of the country's alleged involvement on Wednesday, but no one had yet made the accusation on the record. CNN is reporting that officials say "hackers routed the attack through servers in countries from Asia, Europe and Latin America, even some in the U.S." More detail from the Wall Street Journal:
An analysis of malware that deleted data on Sony computers shows similarities to other malware used previously by North Korean suspects, including lines of code, encryption algorithms, data deletion methods, and compromised networks, the FBI said.
Investigators also found “significant overlap” between the infrastructure of the Sony attack and other hacking previously linked to North Korea, including Internet protocol addresses that were part of the data deletion malware.
The FBI also found similarities to a cyberattack in March 2013 on South Korean banks and media outlets.
White House spokesman Josh Earnest has said the U.S. will respond in "proportional" fashion to the attack, though it's not yet clear what a proportional response to such an unprecedented type of incitement would entail.