More than 1,000 out of a sample of 13,000 Android applications analysed by German researchers contained serious flaws in their SSL implementations.
In this paper (PDF), the researchers from Leibniz University in Hannover and Philipps University of Marburg found that 17 percent of the SSL-using apps in their sample suffered from implementations that potentially made them vulnerable to man-in-the-middle MITM attacks.
They state that they were “able to capture credentials from American Express, Diners Club PayPal, bank accounts, Facebook, Twitter, Google, Yahoo, Microsoft Live ID, Box, WordPress, remote control servers, arbitrary e-mail accounts, and IBM Sametime”.
In addition, since virus software also uses SSL, “We were able to inject virus signatures into an anti-virus app to detect arbitrary apps as a virus or disable virus detection completely.”
The problems arise because of developers misusing the SSL settings the Android API offers. Examples given by the researchers including apps that are instructed to trust all certificates presented to them (21 of 100 apps selected for a MITM test); 20 of the MITM-tested apps were configured to accepts certificates regardless of its associated hostname (for example, an app connecting to PayPal would accept a certificate from another domain). Other issues included SSL stripping and “lazy” SSL implementations.
Furthermore, the researchers note that a number of apps provided insufficient feedback to users – for example, failing to tell the user whether or not it was using SSL to transmit user credentials.
The researchers say the tool they developed for scanning apps’ SSL implementations, MalloDroid, will be available as a Web app and as part of the Androguard security scanner.
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