North Korea appears to be behind cyber attacks that disrupted dozens of websites in the United States and South Korea according to authorities.

North Korea Likely Behind Cyber Attacks

South Korea’s spy agency, the National Intelligence Service (NIS) said on Wednesday, an organization and possibly a state were behind the attacks in the country and there were indications of “meticulous preparations” for the act.

The NIS did not provide further details, but South Korean news agency Yonhap, quoted parliament members saying they had been briefed by the spy agency, which believes “North Korea or pro-North elements” were responsible for the attacks.

“Malicious programs” were detected targeting 26 U.S. and South Korean websites, including the White House, NIS officials said.

The websites of South Korea’s presidential office, defense ministry, and the National Assembly were jammed with access requests caused by malicious software on Tuesday, disrupting server response to legitimate traffic, South Korea’s Communications Commission said in a statement.

“The attacks consisted of massive harmful traffic to specific sites causing access slowdown or disablement, and some national institutions, banks and media sites have been targeted,” it said.

The attacks left some government websites and online shopping sites down on Wednesday and access to some U.S. government sites within the country appeared to be down, possibly due to security actions in the United States that blocked access from South Korea because of the attacks, local media reported.

The NIS is investigating the incident and will report to the parliamentary intelligence committee on Thursday its findings.