Pierluigi Paganini August 09, 2019

Security researchers at Emsisoft have released a new decryptor tool that allows the victims of the JSWorm 4.0 ransomware to decrypt their files for free.

Thanks to the experts at Emsisoft the victims of the JSWorm 4.0 ransomware can decrypt their files for free.

Like previous versions of the malware, the JSWorm 4.0 ransomware is also written in C++ and uses a modified version of AES-256 to encrypt files.

The malicious code adds the extension “.[ID-][].JSWRM to the filenames of encrypted files. Once encrypted all data it drops the ransom note “JSWRM-DECRYPT.hta” using the following text:

"JSWRM 4.0.2 Your files are corrupted! Identificator for files: [redacted] E-mail for contact: [email protected] Backup e-mail for contact : [email protected] Free decryption as guarantee! Before paying you can request free decryption of 3 files. Total size of files must be less than 5MB (non-archived). Files shouldn't contain valuable information (accept only txt\jpg\png). Attention! Don't try to decrypt it manually. Don't rename extension of files. Don't try to write AV companies (they can't help you). "

Emsisoft release the detailed usage guide for the decryptor that is available here.

In May Emsisoft experts released a free Decrypter tool for the JSWorm 2.0 variant.

In July the company released other free decryptors for the LooCipher ransomware, the ZeroFucks ransomware, and the Ims00rry ransomware.

Pierluigi Paganini

(SecurityAffairs – JSWorm, ransomware)

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