The feature's debut--for self-selected early adopters--involves installing and running an "experimental build" version of the Dropbox software, released Friday, for their Windows, Mac OS X, or Linux PC. The feature had been previewed by Dropbox's VP of engineering, Aditya Agarwal, last month, after an investigation conducted by Dropbox into a spam campaign against its users was ultimately traced to passwords that had been reused by Dropbox users on other sites, from which the credentials had been stolen.
But Dropbox also found that one password-reuse culprit was in fact a Dropbox employee, who'd stored--unencrypted--a copy of some Dropbox users' email addresses in his Dropbox account, which an attacker then accessed and downloaded. In the wake of that breach, some security experts had recommended that all Dropbox users treat any data they uploaded to the service as publicly accessible.
As of Friday, however, Dropbox users can make it more difficult for attackers to access their stored items, by using the "enable two-step verification" feature now displayed on the security tab of their account pages. The sign-up page states: "Two-step verification adds an extra layer of protection to your account. Whenever you sign in to the Dropbox website or link a new device, you'll need to enter both your password and also a security code sent to your mobile phone." Instead of receiving text messages with a one-time log-in password, however, Dropbox users can choose to use a mobile app.
If going the text-message route, here's how to set it up: Users input their cellphone number into the website, receive a six-digit numeric code, and then provide this back to the Dropbox website. The Dropbox website then gives users a unique 16-digit password, together with this admonition: "If you ever lose your phone, you'll need this emergency backup code to disable two-step verification and access your account."
[ Wondering about security of your text messages? See Android And BlackBerry Safer Than iOS For SMS. ]
While any new security features are to be welcomed, early users have suggested that Dropbox's new two-factor authentication system still isn't ready for primetime. "I'm afraid I don't think we're quite here yet with two-step verification," said Dropbox forum "power user" Grant H. Monday in a post to the company's online forums. "Once a Dropbox user enables two-step verification he should be unable to sign into his account without entering a valid code into the sign-in interface. But that doesn't seem to be the case because mobile apps obviously still work, as does the Dropbox website--without any two-step authentication. The infrastructure shouldn't even allow this to happen."
Multiple users have also criticized the current options for regaining access to an account if a user loses his cellphone or forgets her password. "In Google, I have a mobile authenticator app as my primary method for getting codes. But as a backup, I can have Google call me or text me with a code," said Grant H. "Dropbox only allows a mobile app or SMS, but not both. This is actually so serious that I've left off two-step verification for the time being until it's fixed."
"Pro user" David W. agreed, saying that "to have your entire Dropbox account contingent upon you not losing one 16 character password is crazy!"
Obviously, the two-factor authentication feature is still in beta, and Dropbox will no doubt continue to work out the kinks, but it's not the only security enhancement on offer. Dropbox's Agarwal said last month that Dropbox would also be implementing "new automated mechanisms to help identify suspicious activity" and a page that lists all historical log-ins to a user's account. He also said Dropbox was exploring mandatory password changes, for example if a user's password hadn't been changed for a specified period of time, or if it wasn't sufficiently complex.
Seeing any security improvements from the cloud-storage firm is good news. Of course, with Dropbox now competing in the crowded cloud-storage marketplace, it's arguably a business necessity. Indeed, the service competes directly with Apple iCloud, Box.com, Google Drive, and Microsoft SkyDrive.
Meanwhile, services such as SpiderOak and Wuala are offering a "zero knowledge" approach that encrypts client-side data, but gives the service provider no access to the key, thus helping secure the information not just against outside attackers, but any surreptitious law enforcement access demands
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