A bruteforce botnet targeting a wordpress site

One of my wordpress sites has been hit by an organized brute-force login attack originating from a botnet. Since I use fail2ban for wordpress logs with 1 hour bantine, it was interesting observing the bots coming one at a time, triggering a ban almost immediately, and being followed by the next IP immediately, again and again. The attack lasted about one hour and featured about 120 distinct IPs. You can see the spike in the fail2ban graph:

fail2ban-monthThe usernames were the evergreen admin, domain and domaintld.

Update 20160927: more waves of bruteforce logins coming from dozens of different IPs. The real number of IPs is about 1/3 higher, due to the munin graph compression.