1.Download the EPEL repo : rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-3.noarch.rpm 2.Then type the following command : yum install mod_security Note : Mod_security require liblua-5.1.so, If you don’t have this , it will throw an error while installing by yum. –> Processing Dependency: liblua-5.1.so for package: mod_security –> Finished Dependency Resolution mod_security-2.5.9-1.el5.i386 from epel has depsolving problems –> [...]