Prerequisites
Install latest versions (devel) of LibCurl and LibXML2
# yum install libxml2-devel
# yum install libcurl-devel
Download Source Code
Go to https://modsecurity.org/download.html and download the latest Stable Release Quality Source Code for Apache
# wget https://www.modsecurity.org/tarball/2.9.3/modsecurity-2.9.3.tar.gz