Akismet blocks suspicious comments from wordpress blogs. I don't think it does the same with followers. Anyway, followers can't harm you unless they start posting spamming comments. In that case, Akismet will come to the rescue.
You can help WordPress determine spammers for you. You may try to block certain words or phrases which you might find offensive or spammy.
This how to do it:
1) Go to your DASHBOARD.
2) At the right sidebar, find the SETTINGS and click it.
3) A dropdown menu will appear, click DISCUSSION.
4) Just go around that page and figure out which one you can use to help your blog rid of spammers :) Pay attention to the items: he COMMENT MODERATION and COMMENT BLACKLIST.