An IP address, nevertheless, isn’t always a dependable guide to the nationality or geographic location of an Internet user.

On Twitter the hacker posted more info on Tuesday, including four files of reactor-related advice and what appeared to be patterns of facilities, among other stuff.

The KHNP said the content released on Wolsong nuclear power plants and the Gori wasn’t classified and wouldn’t impact security.

The investigation team said it’s also requested help from the FBI to research the servers of US-based Twitter, Yonhap reported.

Officials from the Ministry of Energy , Industry and Trade said the hacker would not be able to damage the reactors.

They said the information released so far seemed to be from the power plants’ operating system, which until April 2013 was connected to the World Wide Web, Yonhap reported.

But KHNP yet established a two-day practice Monday to examine its capability to thwart a cyber attack, following the string of leaks that were on-line.

The exercise came at a time of heightened anxiety about cyber crime after a crippling strike against Sony Pictures which both Washington and Seoul have attributed on North Korea.

There’s been no sign that the North was behind the discharge of the atomic substance.

But Justice Minister Hwang Kyo-Ahn said in parliament that researchers were looking into a potential cyber attack by North Korea.