The apache logfile analyzer, as used by the ONO CronSync service and the ONO Admin application's Security screen.
This will generate lists (arrays) or IP addresses and IP ranges.
This allows to protect HTML content from evil clients in a very simple way - it either lets the content pass unmodified, or it replaces the content by a 404 (Page Not Found) message.
This returns a simple 404 error message, as an HTML code snipplet.
This will test if the User Agent points to an evil bot, or if the client IP address is in an evil range. If this returns 1, then it may be a good idea to limit or block client access.