The data preprocessing step performed by Johnson, where he analyzes user activities within a certain time period to create time-ordered domain sequences for further analysis on sequential patterns, is known as user- specific sessionization. This process involves aggregating all user activities and requests into discrete sessions based on the individual user, allowing for a coherent analysis of user behavior over time. This is critical for identifying patterns that may indicate a watering hole attack, where attackers compromise a site frequently visited by the target group to distribute malware. User-specific sessionization helps in isolating and examining sequences of actions taken by users, making it easier to detect anomalies or patterns indicative of such an attack.References:The CREST materials discuss various data preprocessing techniques used in the analysis of cyber attacks, including the concept of sessionization to better understand user behavior and detect threats.