Py-Dev Threat Intelligence-Ep 2: .r77 Rootkit
Posted Mar 11, 2025 11:59 AM
r77 RootkitFileless Ring 3 Rootkit
r77 is a Ring 3 rootkit that hides everything:
Features:
Files, directories
Processes & CPU/GPU usage
Registry keys & values
Services
TCP & UDP connections
Junctions, named pipes, scheduled tasks
Hiding by Prefix:
Anything starting with "$77" is automatically hidden.
Configuration System:
The dynamic configuration system allows you to hide:
Processes (by PID or name)
File system items (by full path)
TCP & UDP connections (by specific ports)
Execution Flow:
The rootkit resides in system memory and does not write any files to disk. This is achieved through multiple stages.
This graph shows the entire execution flow from installer execution to the rootkit DLL running in every process. The documentation has detailed explanations for each stage.
AV/EDR Evasion Techniques:
AMSI Bypass: The PowerShell inline script disables AMSI by patching amsi.dll!AmsiScanBuffer to always return AMSI_RESULT_CLEAN. Polymorphism is used to evade signature detection.
DLL Unhooking: EDR solutions monitor API calls via ntdll.dll hooks. r77 removes these hooks by loading a fresh copy from disk and restoring the original section, allowing stealthy process injection.
The r77 rootkit is an open-source, user-mode rootkit designed to operate at ring 3. It hides various system artifacts such as files, directories, processes, registry keys, services, and network connections. Its main purpose is to conceal entities prefixed with "$77", rendering them invisible to standard system monitoring tools.
Key Features of r77 Rootkit:
Comprehensive Hiding Mechanism: r77 conceals files, directories, junctions, named pipes, scheduled tasks, processes, CPU usage, registry keys and values, services, and both TCP and UDP connections. Anything starting with "$77" is hidden.
Dynamic Configuration System:
The configuration is stored in:
HKEY_LOCAL_MACHINE\SOFTWARE\$77config
Allows real-time adjustment of hidden elements (processes, files, network connections).
No elevated privileges required, as the DACL grants full access to any user.
Stealthy Installation and Persistence:
Installer (Install.exe): Ensures persistence by injecting into all running processes.
Shellcode (Install.shellcode): Loads the rootkit directly into memory without writing to disk, enhancing stealth and evading static analysis.
Cryptocurrency Mining Campaigns:
Elastic Security Labs reported threat actors leveraging r77 to deploy the XMRIG cryptocurrency miner.
The rootkit's stealth allowed mining operations to run undetected, maintaining persistent control over compromised systems.
Implications and Considerations:
The open-source nature of r77 highlights the dual-use dilemma in cybersecurity. While tools like r77 are invaluable for education and research, they can also be exploited in malicious campaigns.
Recent incidents involving r77 stress the need for strong security practices and vigilance within software supply chains.
For a full understanding of r77's architecture and features, check out the official GitHub repository.
>> r77 Rootkit on GitHub <<
Credits to: bytecode77
