Linux security settings prohibit ping and prevent ddos ​​from sending outbound packets

Mainly talk about two basic practical applications, which mainly involve banning ping (ipv4) and banning udp, that is, banning hackers from using the server to send out DDoS attacks.

1. Disable ping if there is no iptables

echo 1 > /proc/sys/net/ipv4/icmp_echo_igore_all #Open

echo 0 > /proc/sys/net/ipv4/icmp_echo_igore_all #Close

2. Use iptables rules to ban ping

iptables -A INPUT -p icmp --icmp-type 8 -s 0/0 -j DROP

3. Use iptables rules to prohibit the server from sending packets to the outside to prevent DDOS attacks from outside.

iptables -I OUTPUT -p udp --dport 53 -d 8.8.8.8 -j ACCEPT #Allow UDP service IP

iptables -A OUTPUT -p udp -j DROP #Disable udp service

The above ports 53 and 8888 are required for DNS service. If you don’t know the DNS settings of this machine, you can execute the following command to get the IP:

cat /etc/resolv.conf

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