On GitHub, [AyaanB] details buying a cheap Android TV streaming device, looking for, and finding, baked-in malware.
Multiple warnings have been issued by the FBI and CISA regarding malware on media box Android devices. Many devices have been caught participating in botnets providing residential proxies, ad-click fraud, and DDOS services. [AyaanB] sets out to discover if a $30 set-top streaming box is pre-infected with malware, and extracting it – without ever letting the device talk to the Internet or access other devices on the local network.
Picking a device named in the advisories, [AyaanB] discovered that it was, indeed, preloaded with multiple app stores and applications that wouldn’t typically make sense on a set-top TV box. After identifying the serial port test pads and obtaining a low-voltage serial adapter, they were able to gain access to the bootloader and from there dump the contents of the MMC over TFTP.
With the entire filesystem accessible out-of-body, proving it was infected with malware at the factory becomes simple: the malware is signed as a system application, baked onto the system partition of the MMC, granted SELinux exceptions to mark it as a system binary with shell privileges, and has multiple launch scripts to make sure it is executed even if partially removed. With the malware identified, [AyaanB] continues to dig through to uncover the capabilities.
