Iptables

Delete current rules and chains

iptables --flush
iptables --delete-chain

Allow loopback

iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT

Drop ICMP

iptables -A INPUT -p icmp -m icmp --icmp-type any -j DROP
iptables -A OUTPUT -p icmp -j DROP

Allow SSH, HTTP, DNS

#SSH
iptables -A INPUT -s 10.10.10.10/24 -p tcp -m tcp --dport 22 -j ACCEPT

#HTTP/HTTPs
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 80 -j ACCEPT
iptables -A INPUT -p tcp -m state --state NEW -m tcp --dport 443 -j ACCEPT

#DNS
iptables -A INPUT -p udp -m udp --sport 53 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --sport 53 -j ACCEPT
iptables -A OUTPUT -p udp -m udp --dport 53 -j ACCEPT
iptables -A OUTPUT -p tcp -m tcp --dport 53 -j ACCEPT