'Asacub' Trojan Converted To Mobile Banking Weapon

In a sign of the times, what was once a routine data-stealing tool has evolved into a dangerous mobile banking threat.

In another sign that threat actors have begun turning their sights on mobile devices, Kaspersky Labs has uncovered a new banking Trojan targeting Android users in the US, Russia, and Ukraine.

The malware, dubbed Asacub, has apparently been around since last June and was originally used mainly for stealing browser histories, contact lists, and other data from infected devices. In its original form, Asacub was also designed to steal and forward incoming SMS messages to a remote malicious server, turn off the phone screen, and send SMS messages to targeted users on behalf of the device owner.

However, researchers at Kaspersky Lab last fall began coming across new versions of Asacub with features similar to those found in banking Trojans. For example, malicious files in the new versions of the Trojan contained phishing screens with the logos of major European banks.

“Phishing screens were present in all the modifications of Asacub created since September that are known to us, but only the window with bank card entry fields was used," said Kaspersky mobile threats expert Roman Unuchek in a blog post describing the new threat. That means the operators of Asacub plan on targeting only the users of banks whose logos they use, or that a version of the Trojan exists that already does so, he said.

The original data-stealing Asacub has been modified in other ways as well to function more as a banking Trojan. For instance, the malware now supports a much wider range of functions than the original. In addition to uploading browser, contact, and installed application data to a remote server, the modified Asacub can also display a bank phishing window, enable call forwarding, send and intercept SMS messages, and run specified Unstructured Supplementary Service Data (USSD) requests. USSD requests basically allow communication with cellular operators or mobile services without making calls and sending SMS.

This latest version of Asacub supports additional capabilities like tracking and sending current location data, and taking a snapshot using the device camera.

So far, there is nothing to suggest that Asacub has been used to target US consumers. But the logo of a major US bank was spotted on some versions of the malware, suggesting that an attack could be activated at any time, Unuchek said.

Asacub is another signal of what many predict will be an increase in malware attacks against mobile devices in the near future. It is the second banking Trojan targeting Android users that security vendors have warned about in just the past few days.

Last week, Symantec issued an alert on Bankosy, a data-stealing Trojan that, like Asacub, has been modified to target users of certain banks. According to Symantec, the malware is capable of intercepting SMS messages as well as the voice calls that banks sometimes send to customers as a second form of authentication when a consumer tries to log into an account or carry out certain transactions.

In December, FireEye warned of SlemBunk, a family of Android Trojans rigged to look like the legitimate apps of nearly three dozen financial institutions and service providers scattered across North America, the Asia Pacific, and Europe. FireEye described the malware as capable of harvesting the login credentials of users of certain banks and banking-related apps.

And for the first time ever, two Android mobile banking Trojans -- Faketoken and Marcher -- ended up on Kaspersky Labs’ list of the Top 10 banking Trojans of 2015.

Some security analysts believe that application misuse and lost devices still pose the greatest short-term threat to mobile security -- not malware. But the trend has some analysts advocating that enterprises begin taking precautions against mobile malware.

In a Gartner blog post last September, Gartner analyst Dionisio Zumerle noted that the industry has witnessed an increase in “the development of mobile attacks that can be applied across the enterprise, are more realistic, can be exploited remotely and can do greater damage.”

“However, we have yet to see these attacks translate into actual damages for organizations,” he said.

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