I want to DROP more than 200 requests per ip to prevent ddos attack. this is command that i used to detect requests count per ip :

netstat -alpn | grep :80 | awk '{print $5}' |awk -F: '{print $(NF-1)}' |sort | uniq -c | sort -nr

now i want add all ip addresses that made more than 200 requests into IPtables to DROP input and out put.

  • You realize that the point of a ddos is that the requests come from so many different addresses that you can't block them, rather than loads from a few addresses, and that any but the most simple attacks will still send the incoming traffic to saturate your downlink, whether you reply or not?
    – psusi
    Mar 21 '14 at 2:12
  • I think your command lists open parallel connections to port 80 per IP address. That's not the same as request count per IP (over some time), but admittedly still a useful metric once your server has started to slow down and requests keep queuing up.
    – tanius
    Feb 23 '17 at 18:06

Well you can not prevent ddos, and 200 requests is rather trivial.

Best you can do , IMO, is to set limits

sudo iptables -A INPUT -m limit --limit 50/minute --limit-burst 200 -j ACCEPT
sudo iptables -A INPUT -j REJECT

For port 80, use

sudo iptables -A INPUT -p tcp --dport 80 -m state --state NEW -m limit --limit 50/minute --limit-burst 200 -j ACCEPT
sudo iptables -A INPUT -m state --state RELATED,ESTABLISHED -m limit --limit 50/second --limit-burst 50 -j ACCEPT
sudo iptables -A INPUT -j REJECT

You should be able to adjust those limits to your server.

See: http://blog.bodhizazen.com/linux/prevent-dos-with-iptables/

  • Are we supposed to use both set of commands? Sorry if it's a basic question, I'm completely new and have no idea what I'm doing. Feb 17 '19 at 5:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.