Modern Network Intrusion Detection Systems generate vast volumes of low-level alerts, yet these outputs remain semantically fragmented, requiring labor-intensive manual correlation with high-level adversarial behaviors. Existing solutions for automating this mapping-rule-based systems and machine learning classifiers-suffer from critical limitations: rule-based approaches fail to adapt to novel attack variations, while machine learning methods lack contextual awareness and treat tactic-technique mapping as a syntactic matching problem rather than a reasoning task. Although Large Language Models have shown promise in cybersecurity tasks, preliminary experiments reveal that existing LLM-based methods frequently hallucinate technique names or produce decontextualized mappings due to their single-step classification approach. To address these challenges, we introduce RHINO, a novel framework that decomposes LLM-based attack analysis into three interpretable phases mirroring human reasoning: (1) behavioral abstraction, where raw logs are translated into contextualized narratives; (2) multi-role collaborative inference, generating candidate techniques by evaluating behavioral evidence against MITRE ATT&CK knowledge; and (3) validation, cross-referencing predictions with official MITRE definitions to rectify hallucinations. RHINO bridges the semantic gap between low-level observations and adversarial intent while improving output reliability through structured reasoning. We evaluate RHINO on three benchmarks across four backbone models. RHINO achieved high accuracy, with model performance ranging from 86.38% to 88.45%, resulting in relative gains from 24.25% to 76.50% across different models. Our results demonstrate that RHINO significantly enhances the interpretability and scalability of threat analysis, offering a blueprint for deploying LLMs in operational security settings.