A hidden backdoor in the modified version of Android run by nine Samsung Galaxy models could allow attackers to spy remotely on user data - and even snoop on users using hardware such as the GPS system, camera and microphone, according to the Replicant Project, which makes its own, free version of Android.

While working on Replicant, the developers found that the affected models of Galaxy handset - including popular smartphones such as the Galaxy Note 2, Galaxy S3 and Nexus S - shipped with a program that allowed the modem free rein to perform remote operations including remotely monitoring users, and even modifying user data, according to PC World’s report

In a blog post on the Free Software Foundation, Replicant developer Paul Kocialkowski said, "This program is shipped with the Samsung Galaxy devices and makes it possible for the modem to read, write, and delete files on the phone's storage. On several phone models, this program runs with sufficient rights to access and modify the user's personal data."

He said that programs of this sort, “make it possible to remotely convert the modem into a remote spying device. The spying can involve activating the device's microphone, but it could also use the precise GPS location of the device and access the camera, as well as the user data stored on the phone. Moreover, modems are connected most of the time to the operator's network, making the backdoors nearly always accessible.”

Kocialkowski said that the nine models of Samsung device may not be the only ones affected by the backdoor, according to Information Week’s report. Replicant demonstrated the backdoor via a patch which can instruct modems on affected devices to open, read and close a file. It’s not as yet clear what purpose, if any, the backdoor is meant to serve. Replicant claim it would be “relatively easy” for an attacker to exploit.

"We discovered that the proprietary program running on the applications processor in charge of handling the communication protocol with the modem actually implements a back door that lets the modem perform remote file I/O operations on the file system," said Kocialowski. Kocialowski urged Galaxy users to complain directly to Samsung about the backdoor.

At time of writing, Samsung has not released an official statement about the software.