eBay's security experts have determined that it's highly likely that whoever posted confidential information about its members in a company discussion forum this week stole the data via an e-mail phishing scam, an eBay spokeswoman said Thursday.

The perpetrator of the data disclosure on about 1,200 eBay members didn't hack into eBay systems, spokeswoman Nichola Sharpe said in an e-mail interview, reiterating an assurance eBay made when the incident happened on Tuesday.

eBay is working with law enforcement to take action against the fraudster, she said, while declining to answer whether the person has been identified or caught. Because the situation is delicate, eBay can't fully disclose the information it has gathered, she said.

Sharpe also defended eBay's reaction to the incident, in which a malicious user posted members' information like names, addresses, user IDs and, apparently, credit card numbers on the company's Trust & Safety discussion forum.

In a discussion forum thread, some eBay members have criticized the vendor for, in their view, taking too long in shutting down the forum used by the fraudster.

eBay took the Trust & Safety forum offline about an hour after the fraudster began posting the confidential data.

Regarding the credit card numbers, eBay now knows they didn't belong to the affected members and is fairly certain that the numbers weren't valid at all. "We have reason to believe this data was falsified to cause public concern," Sharpe said.

eBay hasn't been able to determine when the phishing scam may have taken place, she said, while declining to comment on whether the data theft may involve more than the 1,200 members whose information was listed.

Sharpe declined to answer whether eBay can or plans to implement changes to its discussion forums so that potentially malicious postings or suspicious activities can be automatically flagged and alerts triggered.

She also declined to comment on whether eBay has any theories on why the fraudster would choose to disclose the stolen data in such a public and brazen manner.

As part of its investigation, eBay has contacted the affected users by telephone.

In an official blog posting Wednesday night about this incident, an eBay staffer urged eBay users to be mindful about phishing scams and how to avoid falling victim to them.

Sharpe said eBay shuts down over two-thirds of phishing spoof sites in under 24 hours.

"There is no silver bullet to stop spoofing and phishing -- these are Internet problems, which is why eBay collaborates with numerous third parties, such as universities, industry leaders, and law enforcement to ensure eBay is a safe, transparent place to shop," she said.

eBay members should always check their "My Messages" queue to verify any e-mail from eBay concerning their account. "If an e-mail affects your eBay account, it's in My Messages. If you get an e-mail that looks like it's from eBay about a problem with your account or requests personal information and it's not in My Messages, it's a fake e-mail," she said.

Suspicious e-mails should be reported to these mailboxes: spoof@ebay.com or spoof@paypal.com.

"Never click on a link or reply to e-mails that ask for personal information. eBay and PayPal will never ask you for your account or credit card details, username, or password in any communications," she said.

It's also advisable for members to change their passwords frequently.

More information about safety measures on eBay can be found on this Web site.