Hackers have infected a Microsoft website and inserted a program capable of downloading pop-up adverts that could contain viruses.
The MSN Korea website, operated by a third-party company on behalf of Microsoft, has since been fixed but the firm is unclear how many users were affected.
"Microsoft learned of a criminal attempt to compromise an MSN Korea property hosted by a third party," said a company spokesperson. "Upon notification of the criminal activity, the Microsoft Security Response Center and MSN response teams immediately mobilized to investigate the incident. Within a few hours of such notification, Microsoft took the appropriate action to resolve the issue and stop any additional criminal activity."
Since Thursday, when the incident occurred, Microsoft has begun working with law enforcement agencies and is seeking to take legal action against those involved. Some reports have indicated that site was vulnerable because patches had not been applied to known vulnerabilities.
The compromise is particularly high profile because Korea is amongst the world's most net-savvy nations. Earlier today SC reported a South Korean official has accused his Communist North Korean neighbours of forming a specialised unit capable of attacking the U.S. Some industry experts, however, rubbished the theory.