Using NXRM 3, you can protect your organization using repository routing rules. These rules can be used to prevent coordinates associated with your organization from being fetched from remote repositories. The regular expression you need varies from ecosystem to ecosystem, because the repository/path structures are different. Blocking specific components that are neither namespaced nor prefixed is easier to do than creating a blocking matcher for every component youve created. The rules are available in the help documentation for routing rules for Nexus Repository 3.”]
Source: https://blog.sonatype.com/namespace-confusion-minimizing-risk-with-nexus-repository