Auto-ban website spammers via the Apache access_log

check-apache-access-log-spammers.sh

#!/bin/bash

#
# Config
#

# if more than the threshold, the IP will be banned
THRESHOLD=100

# search this many recent lines of the access log
LINESTOSEARCH=50000

# term to search for
SEARCHTERM=POST

# logfile to search
LOGFILE=/var/log/httpd/access_log

# email to alert upon banning
ALERTEMAIL=foo@foo.com

#
# Get the last n lines of the access_log, and search for the term.  Sort and count by IP, outputting the IP if it's
# larger than the threshold.
#
for ip in `tail -n $LINESTOSEARCH $LOGFILE | grep "$SEARCHTERM" | awk "{print \\$1}" | sort | uniq -c | sort -rn | head -20 | awk "{if (\\$1 > $THRESHOLD) print \\$2}"`
do
    # Look in iptables to see if this IP is already banned
    if ! iptables -L INPUT -n | grep -q $ip
    then
        # Ban the IP
        iptables -A INPUT -s $ip -j DROP
        
        # Notify the alert email
        iptables -L -n | mail -s "Apache access_log banned '$SEARCHTERM': $ip" $ALERTEMAIL
    fi
done

Can I add 2 simple features in your code?

This is amazing, I modified it a bit for my needs. Very clear comments, thank you very much!