Guessing the answer to common password reset questions is far easier than previously thought, according to a new study by computer science researchers.
In the paper What's in a Name? Evaluating Statistical Attacks on Personal Knowledge Questions (pdf), Joseph Bonneau of the University of Cambridge and two colleagues from the University of Edinburgh show how hackers stand a one in 80 chance of guessing common security questions such as someone's mother's maiden name or their first school within three attempts.
The academics reached their conclusion after analysing 270 million first and last names pairs extracted from Facebook. Online research about a subject or a pre-existing relationship makes the chances of figuring out the answer to password reset questions still easier.
Sarah Palin's Yahoo! webmail account was famously hacked during the 2008 presidential election using publicly available information to determine the answers to webmail password reset questions. The research led by Bonneau shows that even a brute force dictionary attack with no prior knowledge or background research stands an unacceptably high chance of success.
Bonneau, whose research currently focuses on security and privacy in social networks, said that online services need to move away from password reset questions towards more secure approaches, such as setting multiple questions. The issue is important because access to webmail accounts provides a gateway to other even more sensitive information, such as a possible mechanism to break into online banking accounts.
"Asking what was the name of someone's first grade teacher seems like a secure choice," Bonneau told the BBC. "The problem is that there's a tonne of teachers out there named Mrs Smith."
Sending reset passwords via text messages to a mobile phone already associated with an account represents another step towards improved security. ®