TOKYO Shares of Sony Corp (6758.T) fell nearly 4 percent on Friday after the company revealed hackers had stolen data on another 25 million users of its PC games system in the second massive security breach in less than three weeks.
"There is a real concern that trust in Sony's business will decline," Kota Ezawa, analyst at Citigroup Global Markets Japan, wrote in a note.
"The network business itself still only makes a small direct contribution to earnings, but we see a potential drop in hardware sales as a concern."
The latest revelation, announced on Monday by the maker of the PlayStation video game console and VAIO PCs, came just a day after Sony had announced measures had been put in place to avert another cyberattack like that which hit its PlayStation Network, leading to the theft of information on 77 million user accounts.
Tokyo financial markets were closed from Tuesday to Thursday for national holidays.
As of 0112 GMT, Sony shares were down 3.7 percent at 2,230 yen, underperforming a 1.8 percent fall in the benchmark Nikkei average .N225.