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

Android.WannaLocker

Risk Level 1: Very Low

Discovered:
June 9, 2017
Updated:
June 14, 2017 2:45:58 PM
Type:
Trojan
Infection Length:
Varies
Systems Affected:
Android
Android package file
The Trojan may arrive as a package with the following characteristics:

APK: com.android.tencent.zdevs.bah
Version: 1.0


Permissions
When the Trojan is being installed, it requests permissions to perform the following actions:
  • Change the background wallpaper
  • Access information about the WiFi state
  • Allow access to low-level system logs
  • Check the phone's current state
  • Read and write to external storage devices
  • Open network connections
  • Read system settings
  • Prevent processor from sleeping or screen from dimming
  • Access information about networks
  • Modify the current configuration
  • Mount and unmount file systems for removable storage
  • Modify audio settings


Installation
Once installed, the application will display an icon with Chinese text and an image of a character holding a bunch of red flowers.



Once opened, the application changes the icon to an close-up of a handshake with the text: Lycorisradiata. The application also changes the device's wallpaper to this image.




Functionality
The application encrypts files stored on the device’s external storage. The application then asks the user to pay 20 to 40 Chinese yuan via Chinese payment providers QQ, Alipay, or WeChat in order to decrypt the files.

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: Liang Yuan
Summary| Technical Details| Removal

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