File-encrypting ransomware starts targeting Linux Web servers

Malware researchers from Russian antivirus vendor Doctor Web have recently discovered a new malware program for Linux-based systems that they've dubbed Linux.Encoder.1.

Once run on a system with administrator privileges it starts traversing the whole file system and encrypting files in specific directories, including the user's home directory, the MySQL server directory, the logs directory and the Web directories of the Apache and Nginx Web servers.

The malware program encrypts files with certain extensions, particularly those associated with Web applications in different programming languages, images, media and documents. It then leaves a ransom note in every directory that contains encrypted files.

Linux.Encoder.1 uses a strong encryption algorithm and public-key cryptography, making the files hard to recover without backups or paying the ransom.

Unlike consumer PCs or business workstations, Web servers are more likely to have a backup routine configured. However, this ransomware program also encrypts archives and directories that contain the word backup, so it's critically important to regularly save backups to a remote server or offline storage.

It's not clear how the malware is installed on servers, but attacks against Linux systems typically involve brute-force guessing of remote access (SSH) credentials or Web application exploits, such as SQL injection or remote file inclusion, combined with local privilege escalations.