Internet criminals have published a list of stolen names and passwords of more than 400,000 Yahoo users on the internet.

It was found that the hackers exploited Yahoo’s computer systems and accounts of other websites were also compromised. Users of Google Inc, AOL Inc and Microsoft Corp services were among those whose accounts were compromised and the three companies have asked their users to change their passwords.

Yahoo has already issued a statement apologizing to the users for the breach by cyber criminals. The company has seen a difficult year with the stepping down of two of its chief executives and stagnation in revenue growth. Chairman Alfred Amoroso said at the annual shareholder meeting on Thursday that the company had seen a tumultuous year.

Security experts have criticized the company for not enforcing its security against criminals. They say that internet firms like Yahoo should have adequate security measures in order to defend its users against such breaches.

Yahoo spokeswoman Dana Lengkeek said that the criminals were able to steal an old file from Yahoo Contributor Network and managed to breach the security. “We are fixing the vulnerability that led to the disclosure of this data, changing the passwords of the affected Yahoo! users and notifying the companies whose users’ accounts may have been compromised,” she said.