A basic, example iptables file you can use to configure your VPS.

iptables.sh

#!/bin/sh
 
iptables -F
iptables -X
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -A FORWARD -o lo -j ACCEPT
iptables -A INPUT -j ACCEPT -m state --state ESTABLISHED,RELATED
iptables -A FORWARD -j ACCEPT -m state --state ESTABLISHED,RELATED
 
# ping
iptables -A INPUT -p icmp --icmp-type 8 -j ACCEPT
 
# ssh
iptables -A INPUT -s 0/0 -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -s 0/0 -p udp --dport 22 -j ACCEPT
 
# http
iptables -A INPUT -s 0/0 -p tcp --dport 80 -j ACCEPT
iptables -A INPUT -s 0/0 -p udp --dport 80 -j ACCEPT

# https
iptables -A INPUT -s 0/0 -p tcp --dport 443 -j ACCEPT
iptables -A INPUT -s 0/0 -p udp --dport 443 -j ACCEPT

# mysql
iptables -A INPUT -s 0/0 -p tcp --dport 3306 -j ACCEPT
iptables -A INPUT -s 0/0 -p udp --dport 3306 -j ACCEPT

# webmin
iptables -A INPUT -p tcp -m tcp --dport 10000 -j ACCEPT

# imap, imaps, smtp
iptables -A INPUT -s 0/0 -p tcp --dport 143 -j ACCEPT # imap
iptables -A INPUT -s 0/0 -p udp --dport 143 -j ACCEPT # imap
iptables -A INPUT -s 0/0 -p tcp --dport 993 -j ACCEPT # imaps
iptables -A INPUT -s 0/0 -p udp --dport 993 -j ACCEPT # imaps
iptables -A INPUT -s 0/0 -p tcp --dport 25 -j ACCEPT # smtp
iptables -A INPUT -s 0/0 -p udp --dport 25 -j ACCEPT # smtp
iptables -A INPUT -s 0/0 -p tcp --dport 587 -j ACCEPT # smtp
iptables -A INPUT -s 0/0 -p udp --dport 587 -j ACCEPT # smtp
iptables -A INPUT -s 0/0 -p tcp --dport 110 -j ACCEPT # pop3
iptables -A INPUT -s 0/0 -p udp --dport 110 -j ACCEPT # pop3
iptables -A INPUT -s 0/0 -p tcp --dport 995 -j ACCEPT # pop3s
iptables -A INPUT -s 0/0 -p udp --dport 995 -j ACCEPT # pop3s

# 25. Log dropped packets to 
iptables -N LOGGING
iptables -A INPUT -j LOGGING
iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables Packet Dropped: " --log-level 7
iptables -A LOGGING -j DROP

# and save it to the config file
iptables-save > /etc/iptables.up.rules