The modsecurity3 module is the connector between nginx and libmodsecurity,
the engine of ModSecurity 3: it hands each request and response to the
engine and acts on what the rules say.  The rules themselves are not part of
it -- the OWASP core rule set is one place to get them.

This port only installs the module sources.  The module itself is built by
the nginx ports when their MODSECURITY3 option is enabled.