1. Symantec/
  2. Security Response/
  3. Android.Bmaster


Risk Level 1: Very Low

February 3, 2012
February 8, 2012 4:27:26 PM
Infection Length:
195,990 bytes
Systems Affected:
CVE References:
Android package file
The Trojan may arrive as an APK package with the following characteristics:

Service Name


Process Name


When the Trojan is being installed, it requests permissions to perform the following actions:
  • Access information about networks
  • Access information about the WiFi state
  • Access location information, such as GPS information
  • Allow access to low-level power management
  • Allow access to low-level system logs
  • Allows access to hardware peripherals
  • Allows access to install and uninstall shortcuts
  • Allows access to the camera and the camera's flash
  • Allows access to the list of accounts in the Accounts Service
  • Allows an application to delete cache files
  • Allows an application to get information about the currently or recently running tasks
  • Allows an application to modify the current configuration, such as locale
  • Allows an application to open windows using the type TYPE_SYSTEM_ALERT, shown on top of all other applications
  • Allows an application to read or write the secure system settings
  • Allows an application to restart other applications
  • Allows applications to change the Wi-Fi connectivity state
  • Allows applications to discover, pair, and connect to bluetooth devices
  • Allows applications to open network sockets
  • Allows applications to read and write the SYNC settings
  • Allows applications to write the APN settings
  • Allows mounting and un-mounting of file systems for removable storage
  • Change the phone state, such as powering it on and off
  • Check the phone's current state
  • Make the phone vibrate
  • Prevent the processor from sleeping or the screen from dimming
  • Read or write to the system settings
  • Start once the device has finished booting
  • Write to external storage devices

When the Trojan is executed, it downloads a file that exploits the Open Handset Alliance Android Privilege Escalation Vulnerability (BID 48238) and uses it to get root access on the device.

Next, the Trojan starts its own service:

It then collects the following phone and geographical information from the device:
  • CID
  • IMEI
  • IMSI
  • LAC
  • MNC
  • Model Number
  • Package name of the malware
  • Release version

Next, the Trojan posts the above information to a remote location. It then waits for a response from the server and the location of an APK file to download and install. The downloaded APK file is a remote administration tool (RAT) for Android devices.

The Trojan may then perform the following actions on the compromised device:
  • Access pay-per-view video
  • Call premium-rate numbers
  • Send SMS messages to premium service numbers
  • Steal further information from the mobile device


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Cathal Mullaney
Summary| Technical Details| Removal

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