An expert from South Korea agreed that the breadcrumbs leading to North Korea were left deliberately, saying that concealing one's tracks is an easy task for hackers.

MOSCOW, January 8 (Sputnik) – The group of hackers that staged a cyber attack on Sony Pictures in November might have purposely left evidence indicating that North Korea was behind the attack, the Wall Street Journal reported Thursday, citing a former North Korean official.

"People fiercely compete to prove their loyalty," Jang Jin-sung, who allegedly used to work in a North Korean propaganda unit, said, as quoted by the newspaper. The former official explained that hackers must leave evidence of a successful attack to receive a promotion.

An expert from South Korea, engaged in cyberwarfare work in Seoul, agreed that the trace was left deliberately, saying that concealing one's tracks is an easy task for the hackers.

On Wednesday, FBI chief James Comey expressed "very high confidence" that North Korea stood behind the attack, as some evidence indicated that the attackers had tried to use proxy servers to hide the hack, but they failed to do so consistently. Comey also said one could draw parallels between this and similar attacks on South Korean banks in 2013, in which Pyongyang was also suspected.

In November 2014, Sony Pictures Entertainment was attacked by a group of hackers, self-named the "Guardians of Peace." As a result of the massive attack, over 11 terabytes of corporate information were stolen, including employees' passwords, salary details, emails and other sensitive information.

The United States blamed North Korea for the hack, saying it was in retaliation for Sony's plans to release a comedy film called "The Interview," depicting an assassination attempt on North Korean leader Kim Jong Un.