The banking credentials of Android device users are being threatened by a new, self-updating trojan that poses as a one-time password application (OTP).
Once users download the token-generator application from a third-party forum -- the official Android Market is not affected -- attackers can siphon the data right off the phone, according to a McAfee Labs blog post by security researcher Carlos Castillo. The malware, which is mostly targeting users of Spanish banks like Santander and Banesto, appears credible because it disguises itself with the logo and color of the bank in the application.
Castillo said that once the application is launched, a web page appears that “pretends to be a token generator.” Security tokens issued by banks are a series of digits used for authentication purposes, also known as mobile transaction authentication numbers (mTANs). To obtain their token, users are prompted to enter their online banking username and password.
Once the user selects the “generate” option within the app, the malware displays the “fake token,” Castillo wrote. The app can then intercept SMS messages from the bank to the user, through a man-in-the-middle attack, and forward them to the criminal.
Banks often send out mTANs to customers via SMS messages once a transaction has been made or is in process of being completed. Once the malicious application is launched, however, these messages are intercepted and sent off to a third-party server, along with the victim's online banking login information.
The malware is not predominant or widespread yet -- and U.S. users aren't being targeted -- but Castillo said he foresees more financially driven attacks migrating to the mobile platform.
“Android allows the user to enable and disable the installation of applications from non-market applications, which can increase the risk of infection,” said Castillo in an email to SCMagazine.com. “For these reasons, I believe malware authors will continue to try and achieve financial gain from Android users with malicious applications for this platform.”
Dan Guido, CEO of Trail of Bits, a New York-based security firm specializing in incident response, said that as banking apps become available, users will download them.
Third-party markets are a hotbed for malicious malware applications. While Google has the ability to remotely revoke privileges of malicious applications within its market, those downloaded outside of Google's marketplace can easily go unnoticed.
“I don't see these kinds of malware going down in prevalence,” Guido told SCMagazine.com. “I only see them going up as they've been proven successful and they're relatively cheap to create and you can distribute them without going through Google.”
