Gugi Banking Trojan Outsmarts New Android 6 Security

Kaspersky Lab experts have discovered a modification of the Gugi banking trojan that can bypass new Android 6 security features designed to block phishing and ransomware attacks.  The modified trojan forces users into giving it the right to overlay genuine apps, send and view SMS, make calls, and more.  It is spread through social engineering and its use by cyber criminals is growing rapidly: between April and early August, 2016, there was a ten-fold increase in its number of victims.

The Gugi Trojan’s aim is to steal users’ mobile banking credentials by overlaying their genuine banking apps with phishing apps, and to seize credit card details by overlaying the Google Play Store app.  In late 2015, Android OS version 6 was launched, with new security features designed specifically to block such attacks. Among other things, apps now need the user’s permission to overlay other apps, and to request approval for actions such as sending SMS and making calls the first time they want to access them.

Kaspersky Lab anti-malware experts have uncovered a modification of the Gugi Trojan that can successfully bypass these two new features. Initial infection with the modified trojan takes place through social engineering, usually with a spam SMS that encourages users to click on a malicious link. Once installed on the device, the trojan sets about getting the access rights it needs. When ready, the malware displays the following sign on the user’s screen: “additional rights needed to work with graphics and windows”. There is only one button: “provide.”

When the user clicks on this, they are presented with a screen asking them to authorize app overlay. After receiving permission, the trojan will block the device screen with a message asking for ‘Trojan Device Administrator’ rights, and then ask for permission to send and view SMS and to make calls.  If the trojan does not receive all the permissions it needs, it will completely block the infected device.  If this happens, the user’s only option is to reboot the device in safe mode and try to uninstall the trojan, an activity that is made harder if the trojan has already gained ‘Trojan Device Administrator’ rights.

Aside from these security workarounds and a few other features, Gugi is a typical banking trojan: stealing financial credentials, SMS and contacts, making USSD requests and sending SMS as directed by the command server.  To date, 93% of users attacked by the Gugi Trojan are based in Russia, but its number of victims is on the rise. In the first half of August 2016 there were ten times as many victims as in April 2016.

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