Nvidia has suspended its software developer forum after attackers compromised an unknown number of the login passwords used by its 400,000-strong user community.

The company described the breach as affecting “a small proportion” of the users but nevertheless recommended that when the forum returns individuals change their logins.

“Nvidia suspended operations today of the Nvidia Developer Zone (developer.nvidia.com). We did this in response to attacks on the site by unauthorized third parties who may have gained access to hashed passwords,” read a statement on the forum.

The passwords are encrypted and so are not in principle threatened but this assumes that those used are strong enough to survive brute-force recovery attempts by attackers. Some will not be; Nvida also recommended that passwords common to other sites be changed too.

“We are investigating this matter and working around the clock to ensure that secure operations can be restored,” the statement added.

As of Sunday 6pm BST, the developer site had yet to return, extending the disruption to over two days.

The last week has seen several password hacks, including a major incident that compromised 450,000 passwords on the Yahoo Voice VoIP system which were later posted on the Internet in clear text form.

Many have questioned the dismal fact that (unlike Nvidia in the later compromise), Yahoo hadn't encrypted the passwords at all, a clear breach of current minimum security standards.

In June, LinkedIn was hit by a huge password compromise that ended with at least 6.5 million of its users being asked to change their logins. Those passwords were hashed, but inadequately using only SHA-1 and without added 'salting'.

The scale of the problem facing passwords was underlined earlier this month when Dutch telecoms company KPN decided to suspend its ADSL customer portal after noticing that large numbers of its 180,000 business subscribers were still using the default password, 'welkom01'.