Smartphone plays a vital role in day-to-day activities, it has access to sensitive resources such as sensors, camera, Microphones, and GPS. For an end-user, it is crucial to protect the phone from unauthorized access.
The Android phones are the most-popular and most-used phone operating system, starting from Android 6.0 users grant and revoke app permissions at run time for third party applications.
Security researchers from IMDEA Networks Institute, U.C. Berkeley & ICSI AppCensus, Inc discovered that apps can evade the permission model and gain access to the sensitive data without user consent.
The apps can gain access to the sensitive area through both covert and side channels, more than 88,000 apps from U.S. Google play, out of the 1,325 apps found violating the permission systems.
According to the report, side channels present in the implementation of the permission system allow apps to access protected data and system resources without permission; whereas covert channels enable communication between two colluding apps so that one app can share its permission protected data with another app lacking those permissions. Both pose threats to user privacy.
The Attacks are grouped into five different types of covert and side-channel attack to extract the sensitive data from the device.
IMEI (Salmonads & Baidu)
Five apps that developed in third party developers platform Salmonads platform found to contain IMEI, even though they don’t have permission to access it.
Further analysis revealed that the application contains Salmonads SDK that exploits covert channels to read this information. The largest Chinese search engine Baidu uses the same SDK.
Network MAC Addresses
Android protects access to the device’s MAC address by default, researchers observed that apps transmitting the device’s MAC address without having permission to access it.
The Unity cross-platform game engine used in several Android mobile games spotted sending the MD5 hash of the MAC to Unity’s servers.
Router MAC Address
Access to the WiFi router MAC address (BSSID) is protected by the ACCESS_WIFI_STATE permission. Our analysis revealed two side channels to access the connected WiFi router information: reading the ARP cache and asking the router directly.
More than 70 apps sending location data to 45 different domains without having any of the location permissions.
For instance, Shutterfy and EXIF Metadata send precise geolocation including the latitude and longitude to its server, even though the permission was not provided.
“While this app may not be intending to circumvent the permission system, this technique can be exploited by a malicious actor to gain access to the user’s location.”