WP-BlackCheck is an Anti-Spam Solution for WordPress blocking spam using local detection and a centralized Blacklist Service.
The Plugin does not prevent reading of your blog. But if a blocked IP tries to post a comment WP-BlackCheck will block it, displaying a link to the removal request form.
I'd assume that spammers do not authenticate against your blog. The plugin will block your comments if you are not logged in.
Just follow the link to http://www.stargazer.at/blacklist/ and follow the instructions on the page.
Spammers usually hit quite a few servers with their IPs. It's pretty uncommon that you are the only one who has been hit from that IP. Sharing that info prevents Spam on other blogs.
The plugin comes with a file named wp-blackcheck.pot which contains the messages printed. Feel free to translate it into your language and send the .mo and .po file back to me, so I can include it into the next release.