Cephalus Ransomware: Exploits RDP for Home Access

A new ransomware variant, dubbed Cephalus ransomware, has emerged as a sophisticated threat, targeting organizations via compromised Remote Desktop Protocol (RDP) connections.

Cephalus stands out from other ransomware families due to its unique infection methodology and sophisticated evasion tactics. Its operators gain initial access to target networks by exploiting RDP credentials without multi-factor authentication (MFA). The absence of MFA is a security gap that continues to plague many organizations worldwide.

See also: BQTLOCK: A new Ransomware-as-a-Service threat

Cephalus ransomware: How the attack works – Exploitation of legitimate software

Once inside the network, the attackers use the cloud storage platform, MEGA, to extract data before deploying the ransomware payload. The ransomware’s deployment mechanism involves a particularly clever approach using DLL sideloading via legitimate security software components . Huntress analysts identified this technique during investigations of two separate incidents that occurred on August 13 and 16, 2025, where the malware managed to infiltrate organizations using legitimate SentinelOne security products .

The most interesting aspect of Cephalus ransomware, technically, lies in deployment strategy , which exploits a legitimate SentinelOne executable called SentinelBrowserNativeHost.exe. The ransomware operators place this legitimate binary in the user’s Downloads folder, from where it loads a malicious DLL called SentinelAgentCore.dll. This DLL then loads a file called data.bin, which contains the actual ransomware code. In this way, a multi-stage execution chain is created that helps to evade detection.

See also: Colt: Warlock ransomware group sells customer data

Cephalus ransomware: Prevents free data recovery

Upon successful execution, Cephalus ransomware immediately starts preventing system recovery by executing built-in commands. The first command executed is vssadmin delete shadows /all /quiet, which eliminates volume shadow copies that could be used for file recovery. The malware then disables Windows Defender through a series of PowerShell commands that create exceptions for critical system processes and file extensions, including .cache, .tmp, .dat, and .sss files. The ransomware also modifies Windows Registry entries to disable real-time protection, behavior monitoring, and on-access protection features.

At the end of the process, the malware encrypts files, appending them with the .sss extension, and creates recover.txt files containing payment instructions. The ransom notes contain a unique feature – they reference news articles about previous successful attacks, trying to build credibility and create a sense of urgency among victims.

Protection

Organizations can protect themselves by implementing MFA for RDP access, monitoring for unauthorized use of security executables in unusual locations, and maintaining comprehensive endpoint detection capabilities.

See also: Dire Wolf ransomware targets tech companies

Additionally, they should implement basic security practices against ransomware:

• Stay up to date on the latest ransomware trends and tactics used by attackers
• Implement multi-factor authentication (MFA) for all user accounts
• Enable firewall on all devices connected to your network
• Keep sensitive data encrypted
• Update all your devices and systems with the latest security patches
• Conduct regular security audits and penetration testing
• Use strong, unique passwords and change them regularly.
• Limit user access to only necessary systems and information
• Consider using solutions email security for additional protection against phishing attacks
• Have a recovery plan to quickly restore systems in the event of an attack
• Enable the display of file extensions
• Invest in advanced protection solutions
• Use sandboxing for email attachments
• Keep backup copies of your data