Permanent block of IP after n retries using fail2ban

Question

I have a fail2ban configured like below:

• block the ip after 3 failed attempts
• release the IP after 300 sec timeout

This works perfectly and I want to keep it this way such that a valid user gets a chance to retry the login after the timeout. Now, I want to implement a rule where if same IP is been detected as attack and blocked, unblocked 5 times, permanently block the IP and never unblock again. Can this be achieved with fail2ban alone or I need to write my own script to do that?

I am doing this in centos.

Answer 1

There is no default feature or a setting within fail2ban to achieve this. But, you are probably looking for setting up fail2ban to monitor its own log file. It is a two step process...

Step 1

We could need to create a filter to check for BAN's in the log file (fail2ban's log file)

Step 2

We need to define the jail, similar to the following...

[fail2ban]
enabled = true
filter = fail2ban
action = iptables-allports[name=fail2ban]
logpath = /path/to/fail2ban.log
# findtime: 1 day
findtime = 86400
# bantime: 1 year
bantime = 31536000

Technically, it is not a permanent block, but only blocks for a year (that we can increase too).

Anyway, for your question (Can this be achieved with fail2ban alone or I need to write my own script to do that?)... writing own script might work well. Setting up the script to extract the frequently banned IPs and then putting them into /etc/hosts.deny is what I'd recommend.

Answer 2

I believe if you put bantime = -1 in that config section, it is a permanent block.

Answer 3

To expand on Chin's answer this is pretty simple. Just edit the 2 settings in /etc/fail2ban/jail.conf to match your preferences.

 # ban time in seconds. Use -1 for forever. Example is 1 week.
 bantime  = 604800
 # number of failures before banning
 maxretry = 5