A scan I have run against the whole IPv4 address space, looking for Internet-exposed Modbus services.
more here.......http://pierre.droids-corp.org/blog/html/2015/02/24/scanning_internet_exposed_modbus_devices_for_fun___fun.html
more here.......http://pierre.droids-corp.org/blog/html/2015/02/24/scanning_internet_exposed_modbus_devices_for_fun___fun.html