If you install CSF on OpenVZ hardware node, you won’t be able to access VPS. To fix this create a file /etc/csf/csfpre.sh with following content

[root@server12 ~]# cat /etc/csf/csfpre.sh
/sbin/iptables -A INPUT -i venet0 -j ACCEPT
/sbin/iptables -A OUTPUT -o venet0 -j ACCEPT
/sbin/iptables -A FORWARD -j ACCEPT -p all -s 0/0 -i venet0
/sbin/iptables -A FORWARD -j ACCEPT -p all -s 0/0 -o venet0

[root@server12 ~]#

Restart csf, you will be able to access VPS.

csf -r