Double Dose of Android Trojan Malware Hits Online Banking Users

Android malware is off to a running start in 2016. According to the International Business Times, Google just removed 13 apps carrying the Brain Test malware from its Play store. More worrisome, two Trojan deployments — SlemBunk and Android.Bankosy — are now targeting financial apps used by millions of Android owners. Here’s a quick rundown.

Android Trojan Brings Organized Chaos

SecurityWeek reported that Android Trojan SlemBunk is part of a well-organized and still-evolving chain of malware attacks. Security firm FireEye first analyzed the Trojan in December 2015 and found that it targeted 33 banking apps from financial institutions across North America, Europe and Asia-Pacific. Apps infected with the malicious code are downloaded to user devices through both legitimate adult websites and malicious redirection, often disguised as reputable tools such as Adobe Flash Player.

While the malware is still in a state of flux, security researchers now know that it first triggers drive-by downloads to retrieve the SlemBunk dropper app. Next the dropper unpacks the logic required to recover and deploy a downloader, which in turn contacts the command-and-control (C&C) server to grab the final payload.

This longer-than-average chain of events makes it difficult to track origin servers. What’s more, the app lies in wait until a relevant banking process is initiated. Once detected, SlemBunk generates a customized phishing page that convinces users to hand over personal details.

Forward or Back?

One way to solve the problem of attacks like SlemBunk is two-factor authentication. Along with a username and password, banking customers must also enter a one-time code generated when they try to log in, which is sent to their mobile device via SMS. Not surprisingly, however, clever malware-makers discovered a way to intercept these SMS codes and still break the bank, leading some financial institutions to institute a voice-only policy with codes delivered via automated calling services.

According to PCWorld, however, the makers of mobile Trojan Android.Bankosy have also cracked this code and found a way to forward voice-delivered passcodes to a different telephone number. In the Asia-Pacific region, for example, the service code *21*[destination number]# is often used to forward calls.

By combining this code with malware designed to enable silent mode and keep users locked out of their phone during the bank’s passcode call, victims are unaware the two-factor process has been compromised. If malicious actors already have basic login credentials, it becomes a difficult task for users to convince banks they’ve been hacked because, by all accounts, security is working as intended.

The value of Android Trojan malware is on the rise as smartphones and tablets become go-to devices for financial transactions. Both long-chain attacks like SlemBunk and innovative hacks such as Android.Bankosy are looking for new ways to grab user data and leave no trace behind. This double dose of banking malware means users must apply caution in equal measure.

Douglas Bonderud

Freelance Writer

A freelance writer for three years, Doug Bonderud is a Western Canadian with expertise in the fields of technology and...