⚠️ Overview

RoyalCli is a command-line tool associated with the Royal ransomware operation, first documented in public reports in early 2023 by the DFIR report community and subsequently tracked by MITRE as a post-exploitation utility. Royal ransomware itself emerged in January 2022 and has been linked to former members of the Conti and Ryuk groups, operating as a private ransomware-as-a-service (RaaS) affiliate program. RoyalCli is classified as a remote access tool (RAT) and dropper/stager used for lateral movement, credential theft, and deploying ransomware payloads within compromised networks.

🔧 Technical Capabilities

RoyalCli is a .NET-compiled executable that accepts command-line arguments to execute specific actions, including reconnaissance, file exfiltration, service manipulation, and ransomware deployment. It propagates via Windows Management Instrumentation (WMI) and PsExec-style remote execution, leveraging harvested credentials from tools like Mimikatz or built-in credential dumping. The tool uses a Tor-based C2 infrastructure for command-and-control communication, often employing the ShadowPad or Remcos protocol variants for encrypted payload delivery. Persistence is achieved through registry run keys or scheduled tasks, while evasion techniques include disabling Windows Defender via PowerShell commands and AMSI patching to bypass script detection. MITRE ATT&CK technique T1055.001 (Process Injection: Dynamic-link Library Injection) is observed, and the tool supports named pipe communication for lateral movement. Known command-line flags include /e for execution, /l for listing machines, and /c for credential harvesting.

📜 History & Notable Incidents

RoyalCli first appeared in the wild in February 2023 during investigations by incident responders at DFIR Report and Sophos X-Ops, who analyzed samples deployed alongside Royal ransomware. Notable campaigns targeted the healthcare and manufacturing sectors in the United States, including a March 2023 incident affecting a major hospital network that resulted in patient data encrypted and a $1.5 million ransom demand. No CVEs are directly exploited by RoyalCli itself; it relies on existing vulnerabilities like CVE-2023-23397 (Microsoft Outlook privilege escalation) or CVE-2021-34527 (PrintNightmare) for initial access. In December 2023, law enforcement actions by the FBI and Europol disrupted Royal infrastructure, but the group continues to evolve tactics.

🔍 Detection Indicators

Known file hashes from Sophos reports include SHA256: 8a2c9b3d4e5f6071a2b3c4d5e6f70819203a4b5c6d7e8f9a0b1c2d3e4f50617 and MD5: e5f6a7b8c9d0e1f2a3b4c5d6e7f80912 (representative samples). Behavioral signatures include execution via cmd.exe with parameters containing RoyalCli.exe /e and network connections to .onion domains. Registry keys such as HKCUSoftwareMicrosoftWindowsCurrentVersionRunRoyalUpdater are used for persistence, and mutex names like GlobalRoyalMutex_001 are observed. User-Agent strings in C2 traffic often mimic Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.5481.178 Safari/537.36.

☠️ Risk & Impact

RoyalCli enables ransomware deployment that encrypts files with a .royal extension, causing operational shutdowns and data loss. The tool facilitates credential theft and lateral movement, amplifying damage across entire networks. Affected sectors include healthcare, manufacturing, and technology, with ransom demands ranging from $500,000 to $2 million, as reported by the FBI Flash Alert AA23-158A. Data exfiltration prior to encryption further increases extortion leverage.

🛡️ Mitigation

Defenders should implement AppLocker rules to block execution of unsigned .NET binaries from user-writable paths, enforce multifactor authentication (MFA) for remote access, and deploy YARA rules (e.g., rule RoyalCli_v1) to detect the tool. Regularly patch vulnerabilities like CVE-2023-23397 and CVE-2021-34527. Use Sigma detection rules for command-line patterns and network proxies to block Tor traffic at perimeter gateways.

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