SSHGuard tool

Found via a random Google search: SSHGuard.  It’s not available in pkgsrc, but it’s in other BSD packaging systems, and it lists DragonFly on the site as a possible host.  It monitors various services and blocks access to overly aggressive connections using (on DragonFly) pf.  This is similar to scripts discussed here in the past.  It also may be useful in light of the recent FTPd problem.