Cybersecurity researchers have uncovered details about Ragnar Loader, a sophisticated and evolving malware toolkit actively used by Ransomware cybercrime groups, including Ragnar Locker (aka Monstrous Mantis), FIN7, FIN8, and Ruthless Mantis (ex-REvil).
According to Swiss cybersecurity firm PRODAFT, Ragnar Loader plays a crucial role in maintaining access to compromised systems, enabling attackers to remain embedded in networks for extended periods.
“While it is linked to the Ragnar Locker group, it’s unclear whether they own it outright or lease it to others,” PRODAFT stated. “What is clear is that its developers are constantly improving its modularity and detection evasion techniques.”
First documented by Bitdefender in August 2021, Ragnar Loader—also known as Sardonic—was initially used in an unsuccessful attack by FIN8 targeting a U.S. financial institution. However, evidence suggests the malware has been in circulation since 2020.
How Ragnar Loader Works
Ragnar Loader is engineered to establish long-term footholds within a target environment while leveraging an arsenal of evasion techniques to maintain stealth. Some of its most notable capabilities include:
- Execution of PowerShell-based payloads to launch attacks.
- Encryption and encoding methods (such as RC4 and Base64) to conceal malicious operations.
- Sophisticated process injection techniques for persistence and stealth.
By employing these tactics, Ragnar Loader ensures its continued presence within compromised systems while remaining undetected by security tools.
Ragnar Loader is distributed to affiliates as an archive file package containing multiple malware components. These components enable the following:
- Reverse shell access
- Local privilege escalation
- Remote desktop access
Additionally, the malware facilitates direct communication with attackers via a command-and-control (C2) panel, allowing them to exert complete control over infected systems.
Typically deployed via PowerShell scripts, Ragnar Loader integrates multiple anti-analysis techniques to:
- Obscure control flow logic
- Detect and bypass security software
- Maintain stealth while executing malicious operations
It can also execute DLL plugins and shellcode, enabling file exfiltration and network lateral movement via additional PowerShell scripts.
The Linux Component: Remote Access via ‘bc’
A key feature of Ragnar Loader is its Linux executable, named “bc”, which enables remote access to infected devices.
Why ‘bc’ Matters
- It allows attackers to execute command-line instructions remotely.
- It mirrors techniques used by QakBot and IcedID, facilitating network persistence.
- It is particularly effective in isolated enterprise environments, where security controls restrict traditional malware activity.
“This technique is widely used by cybercriminals targeting enterprise networks, as such devices are often network-isolated,” PRODAFT noted.
The evolution of Ragnar Loader highlights the growing complexity of modern ransomware threats. With advanced obfuscation, encryption, and anti-analysis tactics, this toolkit is a powerful enabler for cybercriminal groups.
Key Techniques Used by Ragnar Loader
- PowerShell-based payload execution
- RC4 and Base64 decryption routines
- Dynamic process injection
- Token manipulation for privilege escalation
- Lateral movement via pivoting file
The emergence of Ragnar Loader showcases the increasing sophistication of ransomware operations. As cybercriminals enhance their stealth, persistence, and evasion capabilities, organizations must adopt proactive security strategies to mitigate risks.
Defensive Measures Against Ragnar Loader Ransomware
- Implement strong endpoint security solutions to detect stealthy malware.
- Restrict PowerShell execution to limit unauthorized script deployment.
- Monitor network activity for signs of C2 communication and unusual process behavior.
- Regularly update security controls to prevent lateral movement within enterprise environments.
With Ragnar Loader’s growing adoption among cybercrime groups, businesses must remain vigilant against persistent threats, modular malware, and evolving ransomware tactics.
