--- fail2ban/iptables-allports.conf     2011-04-02 03:59:01.178912076 +0200
+++ /etc/fail2ban/action.d/iptables-allports.conf       2011-04-02 15:11:47.441713873 +0200
@@ -13,9 +13,12 @@
 # Notes.:  command executed once at the start of Fail2Ban.
 # Values:  CMD
 #
-actionstart = iptables -N fail2ban-<name>
+actionstart = ( flock -x 200
+              iptables -n -L fail2ban-sshd &> /dev/null && exit 0
+              iptables -N fail2ban-<name>
               iptables -A fail2ban-<name> -j RETURN
               iptables -I INPUT -p <protocol> -j fail2ban-<name>
+              ) 200>/var/lock/fail2ban-iptables-allports
 
 # Option:  actionstop
 # Notes.:  command executed once at the end of Fail2Ban