Trojan:Android/Zsone.A

Classification

Malware

Trojan

Android

Trojan:Android/Zsone.A, Trojan:Android/Zsone.A, Zsone, Zsone.A

Summary

Trojan:Android/Zsone.A sends SMS messages to premium-rate numbers related to subscription for SMS-based services.

Automatic action

Once the scan is complete, the F-Secure security product will ask if you want to uninstall the file, move it to the quarantine or keep it installed on your device.

Manual removal

Trojan:Android/Zsone.A can be uninstalled by following the steps below:

  • Go to Settings
  • Go to Applications
  • Go to Manage Applications
  • Select the application
  • Press "Clear data"
  • Press "Uninstall"
  • Select "OK" when asked for confirmation and wait

Suspect a file is incorrectly detected (a False Positive)?

A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:

  • Check for the latest database updates

    First check if your F-Secure security program is using the latest detection database updates, then try scanning the file again.

  • Submit a sample

    After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.

    NOTE If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.

  • Exclude a file from further scanning

    If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.

    Note You need administrative rights to change the settings.

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Submit a sample

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Technical Details

The detection Trojan:Android/Zsone.A identifies a number of trojanized applications that were found on the Google Android Market in May 2011.

At the time of writing, these applications were already removed from the official Android Market, but could still be found in various forums and unofficial Android application distribution sites, most commonly catering to users in mainland China.

Installation

On installation, the affected applications display the following permissions requests:

Payload

Trojan:Android/Zsone.A's malicious routine starts when the application itself is launched. On the fifth click/action performed in the app, Zsone.A's SMS-sending payload is triggered.

The trojan will silently send SMS messages to the following hard-coded premium-rate phone numbers:

  • 10626213
  • 10621900
  • 106691819
  • 1066185829
  • 10665123085

The SMS messages observed so far contain the following text strings:

  • aAHD
  • 921X1
  • 921X2
  • 28AHD
  • 95pAHD
  • M6307AHD

These strings are used within Chinese mobile networks for subscribing to various paid SMS services. The trojan's behavior may result in registering the user's device to a service, thereby incurring unsolicited charges.

The trojan hides its SMS-sending activity from the user by aborting SMS messages received from the following numbers:

  • 10086
  • 10000
  • 10010
  • 1066133
  • 10655133
  • 10621900
  • 10626213
  • 106691819
  • 1066185829
  • 10665123085
  • 10665123085

Zsone.A maintains a record of its SMS-sending status in an XML file in the shared preferences folder. When an SMS message is sent, the trojan saves a 'Y' ('Yes') in the XML file.

Other variant

  • Trojan:Android/Zsone.C