o-Net, the Internet service provider unit of Japan's Sony, alerted customers an intruder broke into its system and stole virtual points worth $1,225 from account holders.

This latest setback comes after personal information of some 100 million Sony user accounts was stolen last month when its online gaming systems, the PlayStation Network and Sony Online Entertainment, were hacked.

Security experts said there were not surprised the electronics company has yet to clean up weaknesses in its massive global network. Earlier this week, Sony shut down one of its websites set up to help millions of users change their passwords after finding a security flaw.

"Sony is going through a pretty rigorous process and finding the holes to fill," said Josh Shaul, chief technology officer for computer security firm Application Security Inc.

"The hackers are going through the same process and they're putting their fingers in the holes faster than Sony can fill them."

Sony announced the latest theft on its So-Net homepage in Japanese on Thursday.

"What we've done is stopped the So-Net points exchanges and told customers to change their passwords," So-Net said in a statement to consumers.

About 100,000 yen was stolen from accounts that were attacked. The company said there was no evidence other accounts in the online system had been hacked.

"At this point in our investigations, we have not confirmed any data leakage. We have not found any sign of a possibility that a third party has obtained members' names, address, birth dates and phone numbers."

Security experts have told Reuters Sony's networks around the world remain vulnerable to attack.

Sony's string of security problems could be attracting more hackers to attack its networks.

"I think it's now 'I'm a hacker and I'm bored,' let's go after Sony," Shaul said.

Sony in the United States did not immediately respond for comment on Friday.

The Wall Street Journal first reported the story.