Adding “File Does Not Exist” Filter To Fail2Ban: Ubuntu 12.04 LTS

Ok so here is a quick post to a common question… adding a filter to fail2ban for bot/scanners searching for files, folders or simply doing recon which can result in exploit discovery, this filter will automatically block a visitor/bot after 4 attempts to scan for a file that does not exist on your domain/server.

like always… BASH IN! (lol…)

sudo bash

First Lets create a new entry in our jail.local file…

vim /etc/fail2ban/jail.local

 

copy the following text after the last apache entry…

[apache-nofile]
enabled = true
port = http,https
filter = apache-nofile
logpath = /var/log/apache*/*error.log
maxretry = 4

 

Now that we have added the entry into our jail.local we proceed, change to the filter.d directory, in this folder you will see lots of other pre-configured filters

cd /etc/fail2ban/filter.d

 

instead of creating a new filter file simply copy another, this will make the next step easier…

cp /etc/fail2ban/filter.d/apache-auth.conf /etc/fail2ban/filter.d/apache-nofile.conf

 

find the line identical to the one below (Line 23)

failregex = ^%(_apache_error_client)s user .* (authentication failure|not found|password mismatch)\s*$

 

replace it with the following one.

failregex = [[]client <HOST>[]] File does not exist:

 

At this point your pretty much done, close the file and restart fail2ban

service fail2ban restart

 

Comment if you have questions, like my post if you find it helpful :)

 

 

 

 

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