The recent hacking attack against Sony Pictures this week is said to have North Korean involvement all over it, according to a Bloomberg report.

Bloomberg's sources say the malware used in the digital attack against the entertainment company was discovered to contain Korean language in its code. The security breach also mirrored significant similarities to other attacks that destroyed data and compromised the systems of several South Korean banks last year.

The cyber attack against Sony led to online leaks of four upcoming movies, as well as temporarily disabling the company's computer network. The four films are "Annie", "Mr. Turner", "Still Alice", and "To Write Love On Her Arms". These four films have been leaked onto file-sharing websites and made available for downloading.

A fifth film, Brad Pitt's "Fury", was also leaked as an aftermath of the attack and is also available for downloading on file-sharing sites. It is estimated that around 888,000 IP addresses have already accessed "Fury" since it was leaked last week.

The cyber attack occurred just a month before Sony was scheduled to release its film "The Interview", a comedy about two journalists who are recruited by the CIA to assassinate Kim Jong Un, reports Business Insider. The North Korean government had sent a letter of protest against the film to U.N. Secretary-General Ban Ki-Moon, calling it an "undisguised sponsoring of terrorism, as well as an act of war."

Sony's websites went down last Monday, displaying images of a red skull with a "Hacked by #GOP" caption before the company's network totally crashed.

The Federal Bureau of Investigation has issued a five-page report saying that the hackers have used malware "to launch a destructive cyberattack in the United States," reports Reuters. The FBI report said the malware attack is seen to be able to overwrite data on company servers while simultaneously knocking out networks.

"The overwriting of the data files will make it extremely difficult and costly, if not impossible, to recover the data using standard forensic methods," the report said. The FBI has sent the report to several U.S. companies, with the request that the recipients not share the information contained within.