looks like the previous update was not enough in terms of preventing spam. In the updated version you will now find a new function. If you are logged in as the admin, at the bottom you will find a button “Ban custom IP”. Using this button you can specify your own IP you want to ban and – most importantly – I made it so that you can also use wild cards, so for example XXX.XXX.XXX.* would ban all IPs beginning with XXX.XXX.XXX.
Hopefully this will help a little bit. Also, if you are updating this plugin, make sure you do not replace the bannedIPs.txt, it would reset your already saved banned IPs.