In the 1976 thriller Marathon Man, Nazi war criminal Dr. Christian Szell tortures runner "Babe" Levy to find out whether it's safe for him to retrieve diamonds stored in a bank deposit box.
"Is it safe?" Szell asks repeatedly. Levy, who doesn't know, can't provide a satisfactory answer.
It isn't safe online, but many people try to achieve some measure of security by keeping their passwords safe in their heads.
"No one can hack my mind," explained one person responding to Google researchers about security practices.
Someone could beat you about the head, a technique euphemistically known as "rubber-hose cryptanalysis," to obtain your secrets. It didn't work in Marathon Man, but it can.
Fortunately, that's not a scenario likely to concern most Internet users. But it demonstrates one of several vulnerabilities that come with trying to remember passwords. There's another issue that may be more relevant: Memory doesn't scale. Trying to remember multiple passwords, if they're as complex as they should be, is a recipe for failure.
Google software engineer Iulia Ion, research scientist Rob Reeder, and user experience researcher Sunny Consolvo set out to explore the difference between security experts and the rest of us. They detailed their findings in the paper "Comparing Expert and Non-Expert Security Practices," which they presented at last week's Symposium on Usable Privacy and Security.
[ Are we our own worst enemies when it comes to security? Read Google: Your Password Security Questions Are Terrible. ]
The difference in security practices between the two groups is striking. The researchers conducted two surveys -- one polling 231 security experts and the other polling 294 Internet users who are not security experts. The latter group was recruited from Amazon's Mechanical Turk crowdsourcing platform.
Among respondents who are not security experts, 42% consider the use of antivirus software to be among the top three things one can do to stay safe online. Only 7% of the security experts polled believe that. Instead, experts prefer keeping software updated. "AV is simple to use, but less effective than installing updates," said one.
When it comes to passwords, only 24% of non-experts polled said they used password managers for at least some of their accounts, compared to 73% of experts. The research paper suggested that non-experts don't trust password management companies. That may not be an entirely unreasonable stance, given the recently reported breach of LastPass. However, experts observed that using a password manager allows people to have passwords that are both strong and unique.
Non-unique passwords present a risk, because attackers will often try passwords they obtain at other websites to find accounts they can hijack. If they're successful, further compromises may follow.
A third point of differentiation between security experts and non-experts is the use of two-factor authentication. Eighty-nine percent of security experts polled said they used two-factor authentication, compared to 69% of non-experts. Some 12% of non-experts said they didn't know whether they use two-factor authentication – which probably means they don't.
Security experts don't always follow their own advice – the report noted that 38% of security experts admitted to clicking on links in email messages from unknown senders, compared to only 12% of non-experts -- so perhaps each group can learn from the other.
The report's major shortcoming, beyond limitations identified in the study, is the absence of data on the results of these security practices. Is it safe if we patch, use a password manager, and employ two-factor authentication? We may think we know, but it's difficult to be certain.