Researchers claimed a banking botnet dubbed Geost has provided attackers access to account information and other data on more than 800,000 Android users since 2016.

As outlined by a new paper released during the Virus Bulletin conference in London by a group that included Czech Technical University in Prague, Argentina’s UNCUYO University and security firm Avast, the campaign involved 13 command-and-control (C&C) servers running hundreds of domains.

A Peek Behind the Curtain of the Geost Botnet

Some basic errors in IT security exposed the banking botnet and even some of the behind-the-scenes conversations among those running it. While using a tool that facilitates private communications called HtBot, the attackers failed to encrypt their data, revealing what they were doing with the botnet, according to the researchers.

The campaign’s approach involved taking legitimate apps within the Google Play store and editing them to include malicious code before making them available on third-party sites for download. Anyone who installed the apps — which included not only banking apps but also games and social media tools — unknowingly allowed malware to monitor their text messages. Geost’s targets included the customers of at least five banks in Eastern Europe and Russia, where banking passwords are sometimes sent via SMS.

If the attackers failed to get account credentials that way, the botnet served up pop-ups within apps asking for login details directly from Android users.

Beyond the technical details behind the botnet, the chat logs from HtBot offered a rare glimpse into the interpersonal relationships among those involved in cybercriminal activity, the researchers noted. Some admitted to feeling “demotivated” despite Geost’s financial success, for example, and one even said he was “not in,” even after being goaded by his colleague to “stand together.”

How to Defend Against Banking Botnets

There is a long history of users innocently installing apps that turn out to be malware or contain malicious code. As always, policies that restrict downloads to trusted sites and app stores are an IT team’s best defense against this type of threat.

Unified endpoint management (UEM) tools provide an extra layer of protection by automating the process of both detecting and remediating any suspicious activity that comes from apps or other sources.