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I've used fail2ban a while now. Today I wanted to learn more about iptables and found iptables-persistent.

After installing, saving and cleanup the iptables rules in /etc/iptables/rules.v4 it looks like this

# Generated by iptables-save v1.6.0 on Thu Aug 24 15:18:11 2017
*filter
:INPUT DROP [107:22965]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [267:46575]
-A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp -m tcp --sport 53 -j ACCEPT
-A INPUT -p udp -m udp --sport 53 -j ACCEPT
-A INPUT -p tcp -m tcp --sport 80 -j ACCEPT
COMMIT
# Completed on Thu Aug 24 15:18:11 2017

My /etc/fail2ban/jail.local contains the following lines

[...]
bantime = 3600
maxretry = 2
[...]
protocol = tcp
chain = INPUT
[...]

After restarting the Server, the fail2ban rule is appended instead of inserted at the top.

Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:22
ACCEPT     tcp  --  anywhere             anywhere             tcp spt:domain
ACCEPT     udp  --  anywhere             anywhere             udp spt:domain
ACCEPT     tcp  --  anywhere             anywhere             tcp spt:http
f2b-sshd   tcp  --  anywhere             anywhere             multiport dports 22

If I type in a wrong login, I get banned and end in jail. But the fail2ban rule is at the end of the input chain, so I can still try and login if I use the correct login information.

How can I ensure that fail2ban is inserted at the top of the chain?

Thanks

0

create a chain BANS (iptables -N BANS) inserted at the top of the input chain (iptables -I INPUT 1 -j BANS) and then set chain=BANS in fail2ban.

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