SECI is a knowledge management model with four phases: Socialization, Externalization, Combination, and Internalization. It describes how tacit knowledge moves between people and documents, then back into practice. In cyber security, this matters because effective defense depends on turning analyst experience, incident notes, and operator intuition into usable procedures, detection rules, and training material.
Security teams use SECI when they share lessons from phishing investigations, write runbooks, combine threat intelligence from multiple sources, and train staff until the process becomes routine. The same pattern can appear in attacks: criminal groups may socialize tradecraft informally, externalize it into checklists or scripts, combine stolen data and public research, and internalize the resulting methods across the group. For defenders, SECI is useful because it highlights where knowledge is trapped, outdated, or too dependent on individuals, which is a common source of operational risk.