An unidentified group of hackers has released details of tens of thousands of US troops to websites, according to the South Korean press.
The hacking attacks were carried out on the anniversary of the start of the Korean War in 1950. They brought down the main websites of South Korea's presidential office and some local newspapers.
The hackers claimed that they had secured and released publicly personal details of more than two million South Korean ruling party workers and 40,000 US troops, including those stationed in South Korea.
Data was posted on different sites across South Korea. The legitimacy of the information could not be verified.
The Korean Communications Ministry has launched a probe into the nature of the attacks and declined to comment the details of the data.
More than 28,500 US troops are stationed in South Korea where North and South Korea remain technically at war after the 1950-53 conflict ended in a truce, not a peace treaty.
Details included dates of birth and ranks of 40,000 U.S. troops including members of the 25th Infantry Division and the 3rd Marine Division.
North Korea is believed to be running a large corps of computer experts aimed at hacking into the networks of governments and financial institutions. So far it has not put its hand up to claim the hack was one of theirs.
At the moment its propaganda wing is having a field day with Snowden's revelations of mass surveillance operations by the National Security Agency.