The Zitmo Trojan, which has been used by the ZeuS criminal gang to steal banking information, was confirmed to be on Android devices by security firm Fortinet last week. In a blog post on the company's website, senior antivirus analyst Axelle Apvrille said that the Trojan poses as a banking activation application and then once installed sniffs out SMS sent from the bank to the user. It then combs through the SMS to pull out the mobile transaction authentication number (mTAN) that is used as a one-time password to complete mobile banking transactions.
As outlined by the S21Sec security blog last year when the Trojan first made appearances on other mobile operating systems, the Trojan is a clever way to sneak around banks' two-factor authentication systems for performing mobile transactions. First, ZeuS-created malware must obtain a person's bank account user name and password. From there, it acquires the user's cellphone number and sends an SMS purporting to be from the bank that contains a malicious application posing as an online banking app. Once this app is installed, it sniffs all incoming SMS for mTANs that it can use to perform transactions on the user's account.
"In the background, it listens to all incoming SMS messages and forwards them to a remote Web server," explains Apvrille. "It's simple, but just enough for the ZeuS gang to grab your banking mTANs."
Although the Zitmo Trojan is a potentially expensive headache for Android users, it isn't at all unique to Android devices and is unrelated to security issues Android has had in the last year with its online Android Market application store. The most high-profile problem came in March when Google removed around 50 applications from the Android Market that contained malicious code. Google has long had a policy of allowing any developer to post mobile applications on the Android Market and relying on users to flag malicious apps for the company to remove.
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