Yoshikada ransomware, another malicious implementation for AES cipher

Yoshikada, a ransom trojan detected in December 2017, is now among the top extortion viruses. Meanwhile, little is known as regards its origin. Descriptions available so far do not seem to be original, in their majority. Many are obviously generic as they describe Yoshikada as adware that displays popups, banner ads, redirects. Any such impacts do not pertain to ransomware in general and Yoshikada in particular.

yoshikada ransom note

yoshikada ransom note

The infection applies AES cipher to scramble the data on the host machine. It is a well-elaborated, strong method; AES is adopted in the USA as an official standard for the government. In the case of official use, this ensures the data is safe towards attempts of unauthorized access aimed at seizure. That is to say, even though a malefactor takes hold of data, the encryption ensures the data is gibberish unless and until you apply the appropriate decryptor.

In the case of Yoshikada ransomware applying the AES algorithm, it is the authorized holder of data who suffers the loss of access to the information. The crooks invade the holder’s machine with trojan using a variety of methods, ranging from spamming to repacked installers and direct introduction via cracked RDB-configuration.
The installation creates an .exe file, the names currently classified as random, stored in random directory. The installation is followed by scanning. The latter identifies the data to be encrypted. This ensures the data of value for the users is most likely to be encrypted whereas system and networking files remain as is. The main reason for such an exemption is the ransom note dropped by the rogue. This reads, in particular, as follows:
‘Your documents, photos, databases and other important files have been encrypted cryptographically strong, without the original key recovery is impossible! To decrypt your files you need to buy the special software – “YOSHIKADA DECRYPTOR…’

Files encrypted by Yoshikada Decryptor

Files encrypted by Yoshikada Decryptor

The encryption modifies target files with a symmetric key. This entails a single key decrypts and encrypts the files concerned. However, the key, once used to encrypt the data on the host machine, itself is typically encrypted with asymmetric encryption. This means the key needed to decrypt the decryptor is not available on the host machine.
The files affected by Yoshikada also have their names modified with extra extension reading .crypted_yoshikada@cock_lu. This is the email the victim is supposed to contact to buy the decryptor. Predictably enough, the ransom is payable in bitcoins. IT security, in general, neither encourages a ransom-based approach to the recovery nor assures the crooks, whether paid or not, are going to decrypt the data. In some cases, master key is made available for free.
To get rid of Yoshikada ransomware and recover the data hit its encryption, proceed with the guidance below.

Automated cleanup to remove Yoshikada virus

1. Click the button to download the stub installer and go through several setup dialogs. Once the tool is up and running, click Start Computer Scan

2. Wait until the cleaner checks the PC for Yoshikada ransomware malicious code. As soon as the scan is completed, the report will list all malware objects spotted in the system. Make sure the entries for detected infections are checked, and select the Fix Threats feature. This will result in malware removal and system remediation, so you should now be good to go.

Restore the encrypted files

Yoshikada encryption is a sophisticated data modification. There is no simple and single solution to cover all the cases. Transferring the ransom as demanded by the crooks is not the way either.Kindly apply the methods outlined below as they have been carefully developed to provide a recovery help for the most severe cases of encrypting assaults.

Data recovery with automatic software

Good news is that the virus actually deals with copies of the files. The originals have been deleted. The removed data still can be restored by virtue of such tools as Data Recovery Pro.

Shadow Volume Copies

As Windows creates backups at given periods of time, a victim is advised to address relevant restore points. Unfortunately, the method cannot apply unless the System Restore had been enabled prior to the invasion. Please also note the recovery returns files as saved before the time associated with the restore point addressed.

  • Previous Versions dialog to target individual files
    One can open Properties for any file. The menu has a tab called Previous Versions. It indicates versions of a file that have been backed up.
    To make use of the feature, right-click an affected file and choose Properties in the drop-down list. Proceed with clicking the above-mentioned tab. You can opt between the Copy or Restore procedures, the former enabling to copy the item into the location specified by the user.

test properties

shadow explorer

Backups and removing remaining traces of ransomware

Prevention is the best cure. If you stick to making regular reserve copies of your data and store those outside your operating system, the impacts by the ransomware are very limited. However, prior to copying the data from backups into the system hit by Yoshikada ransomware, make sure the removal of this virus has completed.

Your manual removal attempts may kill the ransomware in general. In most of the cases, some remnants manage to survive and are still capable of causing a significant damage. Please apply a reliable anti-malware scanner to detect and remove, if applicable, any remaining infections.

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