simple script to rate limit via IPtables incoming requests

rate_limit.sh

#!/bin/bash

DPORT=22         # inbound destination port
PERIOD_SECONDS=5 # duration in seconds that we measure the # of hits
HITCOUNT=4       # acceptable number of hits from same IP in duration

# ref https://debian-administration.org/article/187/Using_iptables_to_rate-limit_incoming_connections

iptables -I INPUT -p tcp --dport ${DPORT} -i eth0 -m state --state NEW -m recent --set

# REJECT instead of DROP otherwise we leave the connection hanging for <TCP TIMEOUT>
iptables -I INPUT -p tcp --dport ${DPORT} -i eth0 -m state --state NEW -m recent --update --seconds ${PERIOD_SECONDS} --hitcount ${HITCOUNT} -j REJECT

# for sport echo what the rules are
iptables -L --line-numbers

#
# delete with
#
# iptables -L --line-numbers
# iptables -D INPUT <line number>

#
# bonus test client
#
##!/bin/bash
#
#for i in `seq 1 5` ; do
#  echo 'exit' | nc <your ip>;