NEW YORK\u2014Usernames and passwords of some of Yahoo\u2019s email customers have been stolen and used to gather personal information about people those Yahoo mail users have recently corresponded with, the company said Thursday.<\/p>\n
Yahoo didn\u2019t say how many accounts have been affected. Yahoo is the second-largest email service worldwide, after Google\u2019s Gmail, according to the research firm comScore. There are 273 million Yahoo mail accounts worldwide, including 81 million in the U.S.<\/p>\n
It\u2019s 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 their personal information and credit and debit card numbers compromised late last year, and Neiman Marcus was the victim of a similar breach in December.<\/p>\n
\u201cIt\u2019s an old trend, but it\u2019s much more exaggerated now because the programs the bad guys use are much more sophisticated now,\u201d says Avivah Litan, a security analyst at the technology research firm Gartner. \u201cWe\u2019re clearly under attack.\u201d<\/p>\n
Yahoo Inc. said in a blog post on its breach that \u201cThe information sought in the attack seems to be names and email addresses from the affected accounts\u2019 most recent sent emails.\u201d<\/p>\n
That could mean hackers were looking for additional email 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.<\/p>\n
\u201cIt\u2019s much more likely that I\u2019d click on something from you if we email all the time,\u201d says Richard Mogull, analyst and CEO of Securois, a security research and advisory firm.<\/p>\n
The bigger danger: access to email accounts could lead to more serious breaches involving banking and shopping sites. That\u2019s because many people reuse passwords across many sites, and also because many sites use email to reset passwords. Hackers could try logging in to such a site with the Yahoo email address, for instance, and ask that a password reminder be sent by email.<\/p>\n
Litan said hackers appear to be \u201ctrying to collect as much information as they can on people. Putting all this stuff together makes it easier to steal somebody\u2019s identity.\u201d<\/p>\n
Yahoo said the usernames and passwords weren\u2019t collected from its own systems, but from a third-party database.<\/p>\n
Because so many people use the same passwords across multiple sites, it\u2019s possible hackers broke in to some service that lets people use email addresses as their usernames. 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\u2019s mail systems, said Johannes Ullrich, dean of research at the SANS Institute, a group devoted to security research and education.<\/p>\n
The breach is the second mishap for Yahoo\u2019s mail service in two months. In December, the service suffered a multi-day outage that prompted Yahoo CEO Marissa Mayer to issue an apology.<\/p>\n
Yahoo said it is resetting passwords on affected accounts and has \u201cimplemented additional measures\u201d 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.<\/p>\n