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Android.Premiumtext

Risk Level 1: Very Low

Discovered:
August 2, 2011
Updated:
August 2, 2011 1:53:08 PM
Type:
Trojan
Infection Length:
Varies
Systems Affected:
Android
Android Package Files
The Trojan generally arrives within a repackaged .apk file from a legitimate application. The package name, publisher, and other details will vary and may be taken directly from the original application.

The following example has been seen used in the wild:

APK: com.battery.improve9.apk
Publisher: Top Battery Application
Name: Battery Improve
Version: 1.0

Note: Since this threat comes bundled with a legitimate application, similar application details may be found in a legitimate version in the Android Marketplace. A repackaged, malicious version of the application can only be found on unofficial marketplaces.


Permissions
When installing the Trojan, it will ask for one or more of the following permissions:
  • Send SMS messages
  • Determine your location through GPS and Internet-based methods.
  • Read SMS or MMS messages
  • Allow full Internet access
  • Allow Bluetooth access
  • Read contact data
  • Read phone state and identity
  • Retrieve a list of running applications
  • Change the WiFi state.
Once installed an icon for the original application will appear. For example:



Note: This icon may also belong to a legitimate application on the Android Marketplace. Malicious versions of the application can only be found on unofficial marketplaces.


Revenue generation
The Trojan then sends SMS messages to premium-rate numbers.

The phone numbers that the threat sends these messages to are either hard-coded into the threat, or downloaded in a configuration file from a predetermined website.


Further actions
These types of Trojans usually contain further functionality besides sending SMS messages. Some of these actions include the following:
  • Gather the IMEI number, phone number, phone name, carrier, and Android version and send it to a remote location.
  • Send a list of installed and running packages to a remote host.
  • Modify WiFi and network settings.
  • Replace the advertisement networks used in some applications with one of the attacker's choosing, and not associated with the developer of the genuine application.

Recommendations

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: Poul Jensen
Summary| Technical Details| Removal

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