[CentOS] CentOS 6.3 - fail2ban not working properly + workaround

Theo Band

theo.band at greenpeak.com
Tue Mar 12 17:57:38 UTC 2013


On 03/12/2013 05:35 PM, Timothy Murphy wrote:
> I'm running fail2ban on my server (under CentOS-6.4)
> and it seems to be running according to
> -------------------------
> [tim at grover fail2ban]$ sudo service fail2ban status
> Fail2ban (pid 31794) is running...
> Status
> |- Number of jail:      1
> `- Jail list:           ssh-iptables
> -------------------------
> I have absolutely no idea how fail2ban works,
> and I'm running it with the default /etc/fail2ban/fail2ban.conf ,
> which seems to set the logfile to /var/log/fail2ban.log .
> Should I actually study how it is meant to be configured?
>
> I just yum-installed it (from Epel, I assume)
> and hope it does its job, whatever that is.
It sets up iptables rules for every jail that is configured (iptables 
-L). You seem to have only the ssh-iptables configured. Check the date 
of the logfile. I noticed that SYSLOG is now used for logging. It used 
to be /var/log/fail2ban.log in the past. I removed the old log file.
If ssh is the only public service you want to protect against brute 
force, then you don't need to setup anything. But have a look in 
/etc/fail2ban/jail.conf and add at least your email address to get a 
notification when it blocks access. There lots of other "jails" that can 
be enabled.
Normally I receive several messages a day. So not receiving them means 
that the service is no longer protecting. Simply because it watches a 
renamed no longer updated version of /var/log/secure:

ls -l /var/log/secure*
-rw------- 1 root root 2130892 Mar 12 18:25 /var/log/secure
-rw------- 1 root root 1374710 Feb 17 01:31 /var/log/secure-20130217
-rw------- 1 root root 1482646 Feb 24 03:09 /var/log/secure-20130224
-rw------- 1 root root 1732930 Mar  3 03:13 /var/log/secure-20130303
-rw------- 1 root root  656454 Mar 10 03:12 /var/log/secure-20130310

Once a week fail2ban stops working as a new secure log file is created 
(logrotate) and it seems to watch the only old name. You will not see 
any error message and status show as running.
But I have no proof that it keeps working with the gamin fix.

Theo






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