I see a lot of failed login attempts by, what I assume are botnets, trying to break in with a non-existent 'admin' username. Through the noise of all the failed (and locked out) attempts, I often can discern certain groups of hostnames that seem to be hijacked en masse. For example, we've seen a load of malicious traffic pumped through vpn999.com's network, which made it easy for us to slice away a large chunk of interference by blocking their entire network from accessing the site.
Unfortunately, WordFence does not allow blocking based on hostname. I'd like to request that feature in a future version. That way I don't have to work with multiple blocking plugins. Right now, I'm using 'WP-Ban' on the side for hostname-based blocking, but I'd like to decrease plugin clutter and this seems like a realistic reason.
If I am so lucky to discover this new feature in a next WF update, many thanks in advance =)