A security gate is a formal checkpoint in the project lifecycle or SDLC where a security assessment must take place before the initiative may proceed. Typical gates sit before the architecture review, before deployment, and before go-live. At the gate you verify that all defined security requirements have been met — for example completed penetration tests, resolved critical findings, or approved risk acceptances. In an ISMS, security gates formalise change control and ensure security remains integral to every stage.