App syncing across devices was poorly implemented and leads to attackers sneaking malicious apps on your phones. 2FA, or Two-Factor Authentication, is regarded alongside biometrics as one of the strongest methods of protecting user data online. A new attack devised by two researchers at a university in Amsterdam shows that weak spots exist in this authentication scheme that open users to attack.
The two, Radhesh Krishnan Konoth and Victor van der Even, said they’ve discovered the flaw back in 2014, alerted Google and other online services, and even presented their findings to a series of banks, but to no avail.
As the researchers explained, because they haven’t gone public until now, many have said that the vulnerability was never dangerous enough to warrant the attention. The two think differently.
App syncing between devices is 2FA’s Achilles heel
As they explain, the attack does not leverage a software flaw, but a design issue with 2FA. Because of a concept called “anywhere computing,” which refers to the ability to sync apps and content across devices, 2FA can be defeated if an attacker gains access to a victim’s PC.
From here, design flaws in the 2FA mechanism of various services allows the crooks to use services such iTunes or the Google Play Store to push malicious apps to a user’s phone without triggering the 2FA authentication system or even show an icon on his homescreen.
Of course, the attacker must also pass malware past Google and Apple and have it listed on their stores, but this has recently started to become a common occurrence.
But still, this also requires for attackers to have full access to your PC, either physically, or through malware that is controlling the device, or has stolen your credentials in order for the attackers to use.
App syncing across devices is not a bad idea, just poorly implemented
Nevertheless, the risk still exists, and the researchers claim that services using 2FA should be very wary of implementing app syncing among different devices.
Asked how they see 2FA services fixing this issue, and especially with Google, where this scheme is used, the researchers said that the best decision is to “move the app installation process (where the user is prompted to accept the app’s permissions) to the mobile device instead of handling it in the browser.”
For more details, you can check out the video below, the BAndroid website, and take a look at the researchers’ paper called How Anywhere Computing Just Killed Your Phone-Based Two-Factor Authentication.