If you followed the tutorial, "How to Install and Configure fail2ban on Ubuntu 10.04 for SSH and Pure-FTPd" then you should have Fail2ban installed and configured  for SSH and Pure-FTPd. You may be curious how to view which IP's are banned or blocked by Fail2ban, or you may wan't to remove some of them from the banned list. To view all addresses that are blocked, run the following command:

sudo iptables -L -n

Banned SSH IP's look like this:

Chain fail2ban-ssh (1 references)

target     prot opt source               destination         

DROP       all  --  192.168.100.100          0.0.0.0/0           

RETURN     all  --  0.0.0.0/0            0.0.0.0/0

Banned ftp IP's look like this:

Chain fail2ban-pure-ftpd (1 references)

target     prot opt source               destination         

DROP       all  --  192.168.100.100         0.0.0.0/0

To remove an IP address from the banned SSH list, run the following command:

sudo iptables -D fail2ban-ssh -s banned_ip -j DROP

To remove an IP address fromthe banned FTP list, run the following command:

sudo iptables -D fail2ban-pure-ftpd -s banned_ip -j DROP

To adjust the time that each IP address is banned for, run the following commands:

sudo vim /etc/fail2ban/jail.conf

Look for the line that begins with "bantime" and modify the value listed (the value is listed in seconds).

If you have any more questions, feel free to leave a comment.