A hacking group known as D33Ds Company posted more than 450,000 usernames and passwords from an unidentified Yahoo (NASDAQ:YHOO) service Thursday.

The group took responsibility and claims the hacking was committed in the name of public service.

“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,” D33Ds said in a brief note posted with the private login information, Ars Technica reports. “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. The subdomain and vulnerable parameters have not been posted to avoid further damage.”

The site on which the hackers posted the information is no longer available.

A Yahoo representative told The Associated Press Thursday that the company is investigating the password breach.