Other than edit history showing a partial IP address, there’s no easy way to do so. And spam is definitely a problem.
Unfortunately, your best bet is instead to restrict posting to Wikidot users only - and then provide an easy way for people to join your site as a member, e.g. using the Join module:
More info here: Wikidot Documentation - Join Module
You can then block users that become a problem through the admin panel for your site. Look under: Admin Panel -> “Security” -> “Blocks” -> Users / IP
The problem with blocking an IP address range (something with a wildcard in it at the end), is that you will likely end up blocking legitimate users as well. So that’s why I’d recommend enforcing people join in order to post, because then you can just block those user accounts.
Community administrators can also delete spammer accounts, to prevent them from impacting others.