Groupthink is a failure mode in which a team settles into repeated consensus and stops questioning its own assumptions. In cyber security, that can happen during incident response, threat modeling, access reviews, or tool selection when disagreement feels disruptive and the same interpretation keeps winning. The result is often blind spots: weak hypotheses go untested, warning signs are minimized, and risky decisions are accepted because they sound familiar.
This matters because attackers benefit when defenders converge on the wrong story. A detection rule may be tuned around an expected tactic, while an unusual attack path is ignored. A secure design review may miss abuse cases if everyone assumes the current process is sufficient. Defenses against groupthink include red-team style challenge, independent review, structured decision records, and inviting dissent early. In practice, healthy security teams treat disagreement as a signal to inspect assumptions, not as a problem to suppress.