Yahoo e-mail passwords stolen - San Francisco Chronicle ~ Electronic Gadgets

User names and passwords of some of Yahoo's e-mail customers have been stolen and used to gather personal information about people those users have recently corresponded with, the company said Thursday.

The Sunnyvale company didn't say how many accounts were affected. Yahoo is the second-largest e-mail service worldwide after Google's Gmail, according to research firm comScore. There are 273 million Yahoo mail accounts worldwide, 81 million in the U.S.

It's the latest in a string of security breaches that have allowed hackers to nab personal information using software that analysts say is ever more sophisticated. Up to 70 million customers of Target stores had personal information and credit and debit card numbers compromised late last year, and Neiman Marcus was the victim of a similar breach in December.

"It's an old trend, but it's much more exaggerated now because the programs the bad guys use are much more sophisticated," said Avivah Litan, a security analyst at technology research firm Gartner. "We're clearly under attack."

Yahoo Inc. said in a blog post that the information sought in the attack appeared to be names and e-mail addresses from the affected accounts' most recent sent e-mails.

That could mean hackers were looking for additional e-mail addresses to send spam or scam messages. By grabbing real names from those sent folders, hackers could try to make bogus messages appear more legitimate to recipients.

"It's much more likely that I'd click on something from you if we e-mail all the time," said Richard Mogull, CEO of Securois, a security research and advisory firm.

The bigger danger: Access to e-mail accounts could lead to more serious breaches involving banking and shopping sites. That's because many people reuse passwords across sites, and also because many sites use e-mail to reset passwords. Hackers could try logging in to such a site with the Yahoo e-mail address, for instance, and ask that a password reminder be sent by e-mail.

Litan said it looks like the hackers are trying to collect as much information as they can. "Putting all this stuff together makes it easier to steal somebody's identity," she said.

Yahoo said the user names and passwords weren't collected from its own systems but from a third-party database.

Because many people use the same passwords across sites, it's possible that the hackers broke in to some service that lets people use e-mail addresses as their user names. The hackers could have grabbed passwords stored at that service, filtered out the accounts with Yahoo addresses and used that information to log in to Yahoo's mail systems, said Johannes Ullrich, dean of research at the Sans Institute, a group devoted to security research and education.

The breach is the second mishap for Yahoo's mail service in two months. In December the service suffered an outage that prompted Yahoo CEO Marissa Mayer to issue an apology.

Yahoo said it is resetting passwords on affected accounts and has "implemented additional measures" to block further attacks. The company would not comment beyond the information in its blog post. It said it is working with federal law enforcement.

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