Current threat analysis processes followed by tier-1 (T1) analysts in a Security Operation Center (SOC) rely mainly on tacit knowledge, and can differ greatly across analysts. The lack of structure and clear objectives to T1 analyses makes operative inefficiencies hard to spot, SOC performance hard to measure (and therefore improve), results in overall lower security for the monitored environment(s), and contributes to analyst burnout. In this work we collaborate with a commercial SOC to devise a 4-stage (network) process to support the collection and analysis of relevant information for threat analysis. We conduct an experiment with ten T1 analysts employed in the SOC and show that analysts following the proposed process are 2.5 times more likely to produce an accurate assessment than analysts who do not. We evaluate qualitatively the effects of the process on analysts decisions, and discuss implications for practice and research.