Prosecutors say the software used in the hacking was similar to that used in a 2009 attack against South Korean websites. (Canadian Press)

South Korean prosecutors say hackers in North Korea hacked into the computer network of a South Korean bank last month.

Prosecutors say the cyber attack on the Nonghyup bank was meant to paralyze its system. They didn't elaborate.

They say the software used in the hacking was similar to that used in a 2009 attack against South Korean websites. South Korea also blamed North Korean hackers for that attack.

Prosecutors found no evidence that the hackers were attempting to make money by hacking into the bank.

They said Tuesday that the hackers apparently prepared for the attack for a long time.