Nimbus Manticore is a 64-bit Windows PE malware compiled with Microsoft Visual C/C++ that emphasizes privilege escalation, lateral movement, and persistence across enterprise networks, exhibiting APT-grade tradecraft mapped to T1068, T1021, T1027, and T1497. Deep Instinct analysis shows multiple layers of obfuscation, with abnormal entropy in the .text and .data sections indicating encoded and encrypted code, dynamic import hiding via GetProcAddress and LoadLibrary*, and sandbox evasion techniques using timing functions such as GetSystemTimeAsFileTime and QueryPerformanceCounter. The malware also loads suspicious modules like unbcl-new6.dll and leverages extensive process and thread creation to execute payloads while blending into system processes. What sets Nimbus Manticore apart is its focus on RPC-based lateral movement and privilege escalation, using APIs like RpcAuthIdentityFree, RpcBindingSetAuth, and RpcImpersonateClient to impersonate legitimate users or services and move between systems without raising obvious alarms. These capabilities allow it to quietly establish footholds across multiple machines, escalate privileges, and position itself for wide-scale impact while evading endpoint and sandbox-based detection. Business impact includes the risk of full enterprise compromise, long-term stealthy espionage or destructive operations, and the failure of traditional EDR and sandbox defenses that many organizations rely on as their primary endpoint controls. In one case, Deep Instinct was reportedly the only vendor on VirusTotal detecting Nimbus Manticore a week after discovery, underscoring a significant detection gap for legacy tools. Mitigation requires combining advanced pre-execution detection, such as deep-learning-based engines, with robust monitoring of RPC activity, anomalous process creation, and unusual DLL loading. Organizations should harden Windows environments by limiting unnecessary RPC exposure, enforcing least privilege for service accounts, and enhancing telemetry collection for threat hunting focused on obfuscation, sandbox evasion, and lateral movement behaviors.
🎯CORTEX Protocol Intelligence Assessment
Business Impact: Nimbus Manticore demonstrates how modern malware can evade widely deployed EDR and sandbox solutions, giving attackers long-term, high-privilege access across Windows estates that support espionage, data theft, or destructive actions. Organizations relying primarily on signature-based or sandbox-heavy defenses may experience silent compromise and expensive, complex response efforts once such threats are finally discovered. Technical Context: The malware’s use of obfuscation, encrypted sections, dynamic imports, sandbox evasion, and RPC-based lateral movement mapped to T1027, T1497, T1068, and T1021 makes it difficult to detect with static signatures or basic behavioral rules. Effective defense requires pre-execution AI models, deep system telemetry, and focused monitoring of RPC impersonation, anomalous DLLs, and cross-host process creation.
⚡Strategic Intelligence Guidance
- Augment existing EDR deployments with pre-execution, ML or deep-learning-based detection capable of identifying heavily obfuscated binaries like Nimbus Manticore before they run.
- Increase visibility into RPC usage by logging and alerting on impersonation calls, abnormal binding patterns, and lateral connections between sensitive Windows hosts.
- Restrict and monitor high-privilege service accounts, minimizing their ability to perform remote RPC operations and enforcing least privilege and credential hygiene.
- Develop threat-hunting playbooks focused on sandbox-evasion behaviors, encrypted PE sections, dynamic import resolution, and suspicious DLL loading across Windows fleets.
Threats
Nimbus Manticore malware
Targets
Windows enterprise networksdomain-joined workstationsWindows servers