A group of hackers on Thursday published a list of over 453,000 log-in credentials on the Internet that were allegedly stolen from a database associated with an unnamed Yahoo service.
The group of hackers calls itself "the D33Ds Company" and claims to have hacked into the database by exploiting an SQL injection vulnerability found on a Yahoo subdomain.
"The subdomain and vulnerable parameters have not been posted to avoid further damage," the hackers said in their release notes.
The leaked information includes MySQL server variables, names of database tables and columns, as well as a list of 453,492 email addresses and passwords in plain text.
The exposed log-in credentials don't only include yahoo.com email addresses, but also email addresses from other public and non-public email providers.
An analysis of the data by Anders Nilsson, chief technology officer at Eurosecure, antivirus vendor ESET's distributor in Scandinavia, revealed that the most common domain names for the leaked email addresses were yahoo.com, gmail.com, hotmail.com and aol.com.
The most common password was "123456" -- used by 1,666 users -- followed by the word "password" -- seen 780 times. In addition, "password" was used as a base word for 1373 passwords.
Even though the hackers did not name the affected Yahoo subdomain, Dave Kennedy, the chief executive officer of security firm TrustedSec, speculated, based on a host name found in the leaked data, that the service is Yahoo Voices, a library of user-generated content formerly known as Associated Content from Yahoo.
Yahoo was not able to immediately confirm the compromise or name the affected service, if any. "We are currently investigating the claims of a compromise of Yahoo! user IDs," Caroline MacLeod-Smith, Yahoo's head of consumer PR in the UK, said via email. "We encourage users to change their passwords on a regular basis and also familiarise themselves with our online safety tips at security.yahoo.com."
"We hope that the parties responsible for managing the security of this subdomain will take this as a wake-up call, and not as a threat," the hackers said. "There have been many security holes exploited in webservers belonging to Yahoo! Inc. that have caused far greater damage than our disclosure. Please do not take them lightly."
If someone's log-in credentials are leaked, there isn't much they can do except to change their passwords as soon as possible, pressure the responsible service provider into improving its security and consider moving to a safer service, David Harley, a senior research fellow at antivirus vendor ESET, said in a blog post on Thursday.