Less than a week after the version 0.5.3, I release 0.5.4 with new features introduced by Debian maintainer, Yaroslav Halchenko. There is too many changes to release directly a stable version.
Please do not forget to remove your previous 0.4.x version before upgrading to 0.5.x and update your configuration file.
fail2ban-0.5.4 is still an unstable version but should work perfectly.
Homepage: http://fail2ban.sourceforge.net