Web sites belonging to Gawker Media abruptly stopped publishing new material on Sunday after mischief-making hackers gained access to the company’s servers.

People who had accounts on the flagship Gawker, Gizmodo, Jezebel and the company’s other Web sites were told to change their passwords because, it said in a statement, “our user databases appear to have been compromised.” Working anonymously, the hackers indicated that they had found more than 1.3 million user names and passwords, though it was unclear whether all of the data had been decrypted.

The hackers published the passwords of some Gawker staff members and mockingly identified thousands of users who had listed their password as “password.”

“We’re deeply embarrassed by this breach,” Gawker said in a statement that was posted across its suite of Web sites on Sunday afternoon.