South Korean authorities issued a cyber security warning after
the websites of several major government agencies and financial
institutions were disabled by apparent hacker attacks.
The websites of the presidential office, Defence Ministry, and the National Assembly were saturated with access requests generated by malicious software on Tuesday, crippling 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.
Some government websites and online shopping services remained down on Wednesday and access to some US government sites from the country appeared to have been disabled.
The commission is working to block the spread of malicious software suspected of causing the attack and has advised users to keep security patches and anti-virus programmes up to date.
Police and prosecutors have begun an investigation into the incidents, South Korea's Yonhap news agency said.
News of the attack caused shares of some online security firms to jump on Wednesday morning, with Ahnlab Inc up by the market's 15% daily limit and ESTsoft Corp climbing 5.31% against the junior Kosdaq market 0.36% slide.
A similar attack on major websites in Estonia two years ago prompted the NATO military alliance to review its response against possible cyber-warfare.