DoubleLocker ransomware for Android, lock your device twice!

Criminals have once again launched a ransomware attack on android based phones this time it is called DoubleLocker.

It is a ransomware program that has been designed to take over your phone and even changes your PIN, which allows the app to be in complete control.

DoubleLocker spreads in the very same way as its banking parent does. It is distributed mostly as a fake Adobe Flash Player through compromised websites.

As we can see in the pic above the fake adobe flash player app installed on a android device.

Once launched, the app requests activation of the malware’s accessibility service, named “Google Play Service”. After the malware obtains the accessibility permissions, it uses them to activate device administrator rights and set itself as the default Home application, in both cases without the user’s consent.

Setting itself as a default home app a launcher is a trick that improves the malware’s persistence. Whenever the user clicks on the home button, the ransomware gets activated and the device gets locked again. Thanks to using the accessibility service, the user doesn’t know that they launch malware by hitting Home.

Activate device administrator? does a flash player really require to erase all data on your phone and be in total control? 

The fraudulent app has been found on several websites.

DoubleLocker also encrypts the user’s data making it nearly impossible to regain control of their own device without paying a ransom. If you happen to become infected with it, experts recommend taking your phone to a professional for servicing and to never give in to paying the ransom.

So how does it bend the user to its will?

DoubleLocker, once executed on the device, creates two reasons for the victims to pay.

First, it changes the device’s PIN, effectively blocking the victim from using it.  The new PIN is set to a random value which the attacks neither store nor send anywhere, so it’s impossible for the user or a security expert to recover it. After the ransom is paid, the attacker can remotely reset the PIN and unlock the device.

Second, DoubleLocker encrypts all files from the device’s primary storage directory. It utilizes the AES encryption algorithm, appending the extension “.cryeye”. “The encryption is implemented properly, which means that, unfortunately, there is no way to recover the files without receiving the decryption key from the attackers.

The ransom has been set to 0.0130 BTC (approximately USD 81 at time of writing) and the message highlights that it must be paid within 24 hours. However, if the ransom is not paid, the data will remain encrypted and will not be deleted.

While the ransom itself isn’t super expensive, it’s still a ransom nonetheless. With DoubleLocker, the creators also designed it to give the fake app administrative privileges.

If any app that isn’t legitimately related to device security or protection/location, it should be an instant red flag to the user if it’s asking to be granted any kind of administrator permissions. In other words, an app for viewing videos doesn’t need that kind of access to a device no matter what.

The fake app, once downloaded and installed, remains inactive but not for long. As soon as you tap the “home” button on the infected device, DoubleLocker becomes instantly activated and the process begins.

It proceeds to lock down the phone and because it was granted administrative permissions, the attackers have the ability to change passwords, change ring tones and ring behavior. They can also wipe all data from the device and even locate it if they wish. Paying the ransom is not a guaranteed fix either so again, avoid giving in to doing that.

How to get rid of it?

In the ransom note, the user is warned against removing or otherwise blocking DoubleLocker: “Without [the software], you will never be able to get your original files back”.

To prevent unwanted removal of the “software”, the crooks even recommend disabling the user’s antivirus software.

Such advice is irrelevant: all those with a quality security solution installed on their devices are safe from DoubleLocker.

The only viable option to clean the device of the DoubleLocker ransomware is via a factory reset.

For rooted devices, however, there is a method to get past the PIN lock without a factory reset. For the method to work, the device needed to be in the debugging mode before the ransomware got activated.

If this condition is met, then the user can connect to the device by ADB and remove the system file where the PIN is stored by Android. This operation unlocks the screen so that the user can access their device. Then, working in safe mode, the user can deactivate device administrator rights for the malware and uninstall it. In some cases, a device reboot is needed.

As for the data stored on the device, there is no way to recover it, as mentioned earlier.

DoubleLocker serves as just another reason for mobile users to have a quality security solution installed, and to back up their data on a regular basis.

Avoid downloading anything outside of a trusted source such as the Google Play Store.

And most importantly don’t allow download from Unknown Sources