Admins eHow SysAdmin Tips & Tricks

October 23, 2019

How to limit the number of incoming connections to a specific port

Filed under: linux,Security — Tags: , , , , — admin @ 11:47 pm

Replace [PORT] & [CON_NUM] with respected values.

iptables -I INPUT -p tcp --syn --dport [PORT] -m connlimit --connlimit-above [CON_NUM] --connlimit-mask 0 -j REJECT --reject-with tcp-reset

July 14, 2009

Limit Connections per IP using mod_limitipconn on cPanel

Filed under: Apache,CentOS,cPanel,General,Security — Tags: , , , , , , — admin @ 9:41 am

one of the problems I had on one of my cPanel servers was that some people were using download managers to download files from server , so hundreds of connections were being ESTABLISHED to Apache and it was becoming like a dos attack and causing Apache to become non responsive.
so here is what I did to limit connections per IP in a cPanel hosting server :
there is an Apache module named mod_limitipconn which will take care of it for us.
first download the latest version of mod_limitipconn from this site : http://dominia.org/djao/limitipconn2.html
decompress and install it.
at current time the latest version is 0.23.

wget http://dominia.org/djao/limit/mod_limitipconn-0.23.tar.bz2
tar jxvf mod_limitipconn-0.23.tar.bz2
cd mod_limitipconn-0.23
/usr/local/apache/bin/apxs -cia mod_limitipconn.c

next step is to add the required configuration to the Apache config file , we can add this directly to the end of httpd.conf file but the problem is that if we do this , the httpd.conf will be overwritten by easyapache so we will use include files to add our config.
login into your WHM panel , and follow the following menu items :
Main >> Service Configuration >> Apache Configuration >> Include Editor
on the Post VirtualHost Include section , choose All Versions from drop down menu and add the following config into it :

<IfModule mod_limitipconn.c>
<Location />
MaxConnPerIP 10
NoIPLimit images/*
</Location>
</IfModule>

then click on update and restart Apache server.
now We are all set 🙂

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