Connect with us

Hi, what are you looking for?



RTM Locker Ransomware Variant Targeting ESXi Servers

A newly identified variant of the RTM Locker ransomware is targeting Linux, NAS, and ESXi hosts.

A newly identified variant of the RTM Locker ransomware appears specifically designed to target ESXi servers, CNAPP and XDR platform provider Uptycs reports.

RTM Locker – RTM stands for ‘Read The Manual’ – is offered under the ransomware-as-a-service (RaaS) business model, with affiliates required to be continuously active, otherwise they would be removed from the operation.

The threat does not target countries in the Commonwealth of Independent States (CIS) region and, unlike other ransomware gangs out there, its operators appear rather focused on staying under the radar instead of making headlines.

Following the analysis of a Windows version of RTM Locker earlier this month, Uptycs took a deep dive into the Linux variant of the threat, which has been observed targeting ESXi/Linux devices, and network-attached storage (NAS) systems.

The malware appears to have been inspired by Babuk ransomware’s leaked code, based on the use of similar random number generation and on employing ECDH in Curve25519 for asymmetric encryption.

“The ransomware binary seems to be geared towards ESXi, because of the two ESXi commands that were noticed at the start of the program. It is statically compiled and stripped, making reverse engineering more difficult and allowing the binary to run on more systems,” Uptycs notes.

RTM Locker’s encryption process relies on asymmetric encryption as an initial step, and then moves to ChaCha20 symmetric encryption.

Advertisement. Scroll to continue reading.

The ransomware creates an ephemeral key (it reads /dev/urandom for that) that is used as a private key during encryption. The private key is also used to generate a public key that is appended at the end of encrypted files. A shared key is also generated, to be used in symmetric ChaCha20 encryption.

The public key and the attacker’s private key are used to obtain the shared secret and restore files.

“Use of both asymmetric and symmetric encryption makes it impossible to decrypt the encrypted files without the attacker’s private key,” Uptycs explains.

Related: Microsoft: Cl0p Ransomware Exploited PaperCut Vulnerabilities Since April 13

Related: Capita Confirms Data Breach After Ransomware Group Offers to Sell Stolen Information

Related: Ransomware Attack Hits Health Insurer Point32Health

Written By

Ionut Arghire is an international correspondent for SecurityWeek.

Click to comment

Daily Briefing Newsletter

Subscribe to the SecurityWeek Email Briefing to stay informed on the latest threats, trends, and technology, along with insightful columns from industry experts.

SecurityWeek’s Threat Detection and Incident Response Summit brings together security practitioners from around the world to share war stories on breaches, APT attacks and threat intelligence.


Securityweek’s CISO Forum will address issues and challenges that are top of mind for today’s security leaders and what the future looks like as chief defenders of the enterprise.


Expert Insights

Related Content


The changing nature of what we still generally call ransomware will continue through 2023, driven by three primary conditions.


Satellite TV giant Dish Network confirmed that a recent outage was the result of a cyberattack and admitted that data was stolen.

Management & Strategy

Industry professionals comment on the recent disruption of the Hive ransomware operation and its hacking by law enforcement.


Several major organizations are confirming impact from the latest zero-day exploits hitting Fortra's GoAnywhere software.


The FBI dismantled the network of the prolific Hive ransomware gang and seized infrastructure in Los Angeles that was used for the operation.


The City of Oakland has disclosed a ransomware attack that impacted several non-emergency systems.

Malware & Threats

Unpatched and unprotected VMware ESXi servers worldwide have been targeted in a ransomware attack exploiting a vulnerability patched in 2021.


The personal and health information of more than 3.3 million individuals was stolen in a ransomware attack at Regal Medical Group.