How do you drive security improvements when you don't own the teams?

Influence without authority comes from making the secure path easier and the value visible: build guardrails and self-serve tooling, partner with a few champion teams to create proof points, tie asks to the team's own goals (reliability, velocity, audit), and use data/metrics to create healthy peer pressure. Escalate sparingly and with evidence; relationships and reciprocity carry most of the work.