Simple script to write a log file suitable for fail2ban

banip.sh

#!/bin/sh

if [ $# -lt 1 ]; then
  echo "Usage: banip <ip>"
  exit 1
fi      

for ip in $*; do
  echo "Banning ip $ip"
  date=`/bin/date +"%Y-%m-%d %H:%M:%S"`
  echo "[${date}] ${SUDO_USER} has requested that ${ip} be banned" >> /var/log/manual-ban.log  
done

jail.conf

[manual-ban]
enabled  = true
filter   = manual-ban
action   = ipfw
logpath  = /var/log/manual-ban.log
findtime = 2
maxretry = 1
bantime  = 86400

manual-ban.conf

[Definition]
 
# Option: failregex
# Notes.: regex to match the password failures messages in the logfile. The
#          host must be matched by a group named "host". The tag "<HOST>" can
#          be used for standard IP/hostname matching and is only an alias for
#          (?:::f{4,6}:)?(?P<host>[\w\-.^_]+)
# Values: TEXT
#
failregex = has requested that (<HOST>) be banned$