Formspring has told its 28 million users to change their passwords following the discovery of a security breach.
A sample of 420,000 password hashes for the question-and-answer website have been posted online, sparking concerns that the entire user base might have been exposed. In response, Formspring disabled users' passwords and applied a reset as a precaution.
In a blog post, Formspring's chief exec and founder Ade Olonoh said that the users' personal information was not in any way associated with the purloined password hashes, adding that the one-way encrypted strings were in any case salted.
Olonoh blames the slip-up on a poorly secured development server linked to a live (production) database.
"Once we were able to verify that the hashes were obtained from Formspring, we locked down our systems and began an investigation to determine the nature of the breach," he said. "We found that someone had broken into one of our development servers and was able to use that access to extract account information from a production database."
Formspring plans to tighten up its hashing mechanisms from SHA-256 with random salts to Bcrypt – based on the blowfish encryption algorithm – in order to bolster security.
Salted password hashes ought to withstand brute force attacks that use rainbow lookup tables.
The exposure follows the LinkedIn breach last month. However early reaction from security watchers, including Graham Cluley at Sophos, is that Formspring has coped better with this breach than LinkedIn did with its hack attack. ®