Ask HN: Mono-Repo or Multi-Repo?

I know that there is a debate about storing all source code in a mono-repo vs multiple repos. I am thinking about it from a security perspective - a separation to multiple repos reduces the risk of source code exposure/leakage and enable more granular access. However, maybe this isn't a high risk as having an insider threat or an account takeover that may inject a malicious code, so setting up codeowners will do the work even in a mono-repo. What are your thoughts?