South Korean Stocks Tumble Amid Computer Attacks

South Korean stocks fell the most in two months, with the benchmark index extending losses in the last minute of trading as a possible cyber attack shut down computer networks at some of the largest banks and broadcasters.

The Kospi index retreated 1 percent to 1,959.41 at the close on the Korea Exchange, its steepest drop since Jan. 15. Samsung Electronics Co., Asia’s biggest maker of chips and flat screens, dropped 1 percent, leading exporters lower. Igloo Security Inc. and Internet security-related companies rallied.

Computer systems of at least three banks and three television stations were shut down, prompting the Defense Ministry to probe whether North Korea is behind the outages. The shutdowns hit companies including Shinhan Bank, Nonghyup Bank, YTN, Munhwa Broadcasting Corp. and Korea Broadcasting System, according to the Korea Communications Commission.

“It’s very unusual to see major banks and broadcasters having computer system errors simultaneously, hurting sentiment at the last minute of trade,” said Heo Pil Seok, chief executive officer at Midas International Asset Management Ltd. in Seoul, which oversees about $5.3 billion. “While there’s some speculation that North Korea may be behind this, nothing has been verified yet and investors need to monitor developments.”

The benchmark gauge fell earlier today on concern Cyprus’s rejection of a bailout plan signals Europe will struggle to contain its debt crisis. The index extended losses in the final 15 minutes of trading on the computer network attacks.

Korea Exchange Inc., the nation’s bourse operator, hasn’t detected any problems with its computer system, spokesman Won Yong Joon, said by phone today. The exchange will keep a close eye on the situation, he said.

Mirae Asset Securities Co. paced declines among brokerages, slumping 5.1 percent, while Woori Investment & Securities Co. dropped 1.7 percent.

Igloo Security, which provides Internet security solutions, advanced 13 percent, while SoftForum Co., which markets data security related products, climbed by the daily limit of 15 percent.

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