Nodewatch is nice tool for OpenVZ server admins, it can prevent DoS and other VPS abuse

homepage: http://vpsantiabuse.com/
install: wget http://deploy.vpsantiabuse.com/nodewatch-install.sh;sh nodewatch-install.sh
config: vi /nodewatch/scripts/nodewatch_config.php
(into configuration file, add license key from vpsantiabuse.com , example key: 57e10608257b8bd1dd94aefdc9a203c11d246774)
uninstall: rm -f /etc/cron.d/vpsantiabuse;/nodewatch/scripts/nodewatch_restart.sh;rm -rf /nodewatch