The Gustuff banking trojan is back with new features, months after initially appearing targeting financial institutions in Australia. Cisco Talos first reported on Gustuff in April. Soon after, the actors behind Gustuff started by changing the distribution hosts and later disabled its command and control (C2) infrastructure. The actor retained control of their malware since there is a secondary admin channel based on SMS.

The latest version of Gustuff no longer contains hardcoded package names, which dramatically lowers the static footprint when compared to previous versions. On the capability side, the addition of a “poor man scripting engine” based on JavaScript provides the operator with the ability to execute scripts while using its own internal commands backed by the power of JavaScript language. This is something that is very innovative in the Android malware space.

The first version of Gustuff that we analyzed was clearly based on Marcher, another banking trojan that’s been active for several years. Now, Gustuff has lost some similarities from Marcher, displaying changes in its methodology after infection.

Today, Gustuff still relies primarily on malicious SMS messages to infect users, mainly targeting users in Australia. Although Gustuff has evolved, the best defense remains token-based two-factor authentication, such as Cisco Duo, combined with security awareness and the use of only official app stores.

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