Advance Auto Parts is looking for an employee who posted confidential financial information about the company on the Internet, and it wants Yahoo to find the culprit.

The Roanoke Valley-based automotive parts retailer has subpoenaed Yahoo, one of the nation's busiest Web sites, for the identity of an employee who posted "highly sensitive sales information" and operational information about Advance on a Yahoo.com finance message board, according to documents filed in the U.S. District Court in Roanoke.

The employee posted entries under the name "aapmanager" on Jan. 7 and Feb. 22 and possibly on other dates. Yahoo has since removed these postings from its message board.

But the messages cost Advance more than $5,000, the court documents state.

"The Confidential Information constitutes material financial information that could potentially be used for insider trading," the documents state.

Advance spokesman Adam Bergman would not release details about the information that the employee leaked on the Internet. He said Advance has not determined whether the poster is a current or former employee of the company.

A lawyer representing Advance did not return a call for comment about the case.

According to the documents, the person used a computer device to access Advance's financial information within its computer database, which extends across state lines. Court documents called the employee's actions an "intent to defraud," and a violation of the computer fraud and abuse act.

It is unclear, however, whether Yahoo can provide Advance with the employee's identity. Although users are asked to give a real name when signing up with the service, there is nothing preventing them from entering "John Doe" or another fictitious name.

What Yahoo can do, however, is provide the IP address -- a unique identifier of the computer used by the poster.

That IP address will lead to the poster's Internet provider, whether it's a local dial-up service, a cable-Internet connection or a business. That provider can then identify who was using that IP address at the time the messages were posted.

A dozen years since Internet use became mainstream, there are well-established exceptions to the notion of Internet privacy. With assistance from the courts, companies have pierced the anonymity that many users think they have on the Internet.

In 2001, for example, Optical Cable Corp. of Roanoke County obtained court help to track down an individual who posted sensitive company information to a Yahoo message board.

The saga began with a salesman's phone call to ask Optical Cable about a report of a layoff posted on Yahoo. The report wasn't true.

When executives examined other postings by the same person, who used the handle "stockinup2001," they saw a purported customer list and purported details of strategic initiatives. Within a week, the company had a court order demanding that Yahoo identify stockinup2001 and warning the poster to stay off the site.

It was never clear how much assistance Yahoo provided in the investigation, which ended with an out-of-court settlement.

Staff writers Jeff Sturgeon and Andrew Kantor contributed to this report.