Security Experts:

Thousands of Sites Infected With Linux Encryption Ransomware

Thousands of websites have already been infected with the Linux file-encrypting ransomware dubbed Linux.Encoder1, security firms reported.

When the existence of Linux.Encoder1 came to light earlier this month, Russian antivirus firm Doctor Web reported that the threat had infected tens of machines, but the number has since increased considerably.

Researchers say the ransomware is designed to infect Linux machines set up to host websites by exploiting vulnerabilities in the Magento e-commerce platform and various content management systems (CMSs).

The malware targets the root and home folders, and directories storing websites, web servers, backups and source code. The extent of the damage caused by the threat depends on the type of privileges it can obtain on the targeted system.

Based on a Google search for the ransom note dropped by Linux.Encoder1, Dr. Web determined that approximately 2,000 websites had been affected as of November 12. A similar Google search conducted by SecurityWeek early on Monday showed that the file was present on roughly 2,600 websites.

Bitdefender believes the number of Linux.Encoder1 infections will continue to rise.

“With most web servers running some Linux OS distribution and shared hosting, it’s safe to assume that if one such website if affected, others sharing the same resources could be affected as well, if they not properly isolated from each other,” Liviu Arsene, Senior E-threat Analyst at Bitdefender, told SecurityWeek. “Since the infection method does not involve any form of social engineering – servers are usually compromised via unpatched vulnerabilities – hosting providers are strongly encouraged to update any outdated software (wordpress, plugins, etc.). More websites will be surely be affected in the immediate future.”

This Linux encryption ransomware uses strong encryption to ensure that victims cannot recover their files without paying the one Bitcoin ($380) ransom. The files are encrypted using the AES-128 algorithm with a key generated locally on the infected device. This key is then encrypted with an RSA public key and since the private key needed for decryption is only stored on the attacker’s machine, it should be nearly impossible to recover files.

However, researchers discovered that the AES key can be easily recovered since it’s generated based on a system timestamp obtained at the moment of encryption. This timestamp can be retrieved from the encrypted file, which has allowed antivirus firms to develop tools that can be used to automatically recover files.

Both Bitdefender and Dr. Web have developed such tools, but Dr. Web’s service is only available to the company’s customers.

While files encrypted by early versions of Linux.Encoder1 can be easily recovered, experts have warned that malware authors might fix the current bugs, making files more difficult to decrypt.

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.