If you use wordpress and you enjoy reading the webserver logs like me, you see many failed login attempts produced by bots trying to guess common passwords for the accounts on your blog. This is bad because:
- if one user has a weak or unsafe password, it will be compromised and your blog probably owned;
- every user enumeration and password guess uses wp-login.php bypassing any caching that you may have, wasting resources that your server may well use to serve content;
I have tried a handful of plugins to limit login attempts, but they all work blocking brute force attempts at the php level.
If you have a dedicated server o a VPS you can use WP fail2ban plugin to write failed login attempts to /var/log/auth.log, then install and configure fail2ban to block offending IPs via iptables. The plugin documentation is straightforward and you should follow the recommended settings.
The key advantage of an iptables approach is that the overhead of blocking brute force bots is very low compared to PHP. The downside is that IP blocking it not very flexible if you really have lots of real users from real networks, so use it if you know what you are doing.
I have found the following settings specially effective:
- raise the bantime from 300 seconds to something higher, like 3600 (1 hour). This has decreased the number of blocked IPs overall.
- rename the admin account and set WP_FAIL2BAN_BLOCKED_USERS in wp-config.php accordingly. This triggers wordpress-hard and blocks bots instantly.
- disable IPv6 on your domains. Unfortunately, fail2ban does not yet support IPv6 (version 0.10 will) and IPv6 bots do exist. Forcing them on IPv4 will let fail2ban block the attacks.
Don’t forget to configure fail2ban properly: to avoid banning your own server’s IP address, add the corresponding entry to the ignoreip line in your jail configuration. Otherwise you risk blocking wp-cron and having “missed schedule” errors in your blog.