A new table was created to save all failed login attempts with
corresponding information on username, ip and useragent. By default
the limit is 50 login attempts within 6 hours per IP. The limit is
relatively high to avoid big problems on sites behind a reverse
proxy that don't receive the forwarded-for value as REMOTE_ADDR but
see all users as coming from the same IP address. But if these
users run into problems a special forwarded-for option is available
to limit logins by forwarded-for value instead of ip.
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