During the development of Replicant project, a free and open-source version of Android a backdoor has been discovered in some of Galaxy devices manufactured by Samsung that allows the modem to perform I/O operations on the file system.
In the modern mobile devices, there’re two processors: the SoC that runs the operating system and applications; and the radio chip that handles communications with the network operator. According to a Replicant developer Paul Kocialkowski, this latter processor runs a Samsung’s proprietary software, manages IPC communication with the modem, which is a backdoor.
The backdoor allows attackers to use the integrated modem as a spying device, doing illegal activities such as turning on the camera and microphone, finding the user’s location via GPS or reading data stored on your smartphone.
In addition, it can also be used to perform remote I/O to the file system, including reading, writing and deleting files from the internal memory.
Although, it’s impossible to build a device in which the modem remains isolated, and in the most of the cases, the radio chip has full control on your smartphone.
Reportedly, the Nexus S, Galaxy S, Galaxy S2, Galaxy Note, Galaxy Nexus, Galaxy Tab 2 7.0, Galaxy Tab 2 10.1, Galaxy S3, and Galaxy Note 2 are found infected with the new backdoor access.
FYI, the offending file has sufficient rights to access and modify your personal data, even if the modem is isolated. However, the free software foundation has also released a patch to remove the backdoor and also urges the users to contact Samsung, asking the company to release the program for free and without backdoors.