As Sony Pictures employees still struggle to get back online, new evidence is emerging that suggests North Korea may be behind the hack. The Wall Street Journal is reporting that researchers investigating the hack have found the malicious code to be almost exactly the same as the code used in a March 2013 attack on a series of South Korean banks and broadcasters, an attack widely believed to have been conducted by North Korea. Re/code had previously reported that Sony was investigating a North Korean connection, but this new analysis is the most definitive evidence unearthed so far.

"We won't give up this attack unless Sony Pictures collapse to the end."

North Korea has been intensely critical of Sony Pictures' upcoming film The Interview, a comedy that follows a plot to assassinate the North Korean leader Kim Jong-un. Sony has already edited out some of the film's more controversial points, including a scene in which Kim Jong-un's face melts off in slow motion in a tribute to Raiders of the Lost Ark. North Korean officials responded to news of the film by saying, "a film about the assassination of a foreign leader mirrors what the US has done in Afghanistan, Iraq, Syria and Ukraine."

Recent statements from the hacking group behind the attacks seem to echo that statement. Because of the group's penchant for communicating through open, unprotected email accounts, it is difficult to verify any message as definitively coming from the group, but one recent message sent to The Verge singled out The Interview as a dangerous and irresponsible move by the studio. Sent from a password-protected email associated with the group, the message read:

Our aim is not at the film The Interview as Sony Pictures suggests. But it is widely reported as if our activity is related to The Interview. This shows how dangerous film The Interview is. The Interview is very dangerous enough to cause a massive hack attack. Sony Pictures produced the film harming the regional peace and security and violating human rights for money. The news with The Interview fully acquaints us with the crimes of Sony Pictures. Like this, their activity is contrary to our philosophy. We struggle to fight against such greed of Sony Pictures.

The concern over regional security and cryptic references to human rights violations mirror earlier North Korean statements, as well as a generally fatalistic message. A later portion of the message reads: "We won't give up this attack unless Sony Pictures collapse to the end."

If the North Korean connection bears out, it would be an extremely unusual development: the first time a Hollywood studio has come under attack from a foreign power. It would also be the first time a foreign power has taken an active interest in piracy, leaking several of Sony's films onto torrent sites. It's too early to say for sure: so far, all the North Korea connections are circumstantial. But even if the culprits are run-of-the-mill criminals, it's already one of the most unusual attacks we've seen in years.

Update, 8:45PM ET: According to Deadline, Sony's computer systems have been fully restored following the hack.