"Within the last 24 hours, we have identified a situation that may have resulted in our subscriber information database being compromised, including password information," Keith Teare, the company's chairman and chief executive officer, wrote in an e-mail distributed to customers.
RealNames said it has no evidence that any of its customers' stolen credit card numbers have been used. The company has beefed up security on its networks since the attack and assigned new password and login information to each of its members. It also called in federal investigators to help resolve the matter, the company said in the e-mail.
The hack appears unrelated to a series of "denial of service" (DoS) attacks launched earlier this week against prominent Web sites including Yahoo, eBay and Buy.com. DoS attacks disable a site by bombarding it with a high volume of information requests in a short period of time, causing the site to crash or grind to a halt.
In some ways the attack on RealNames was more serious, in the sense that hackers actually penetrated RealNames' network and stole sensitive information about its customers.