How to install and configure fail2ban for Debian Jessie:
apt-get install fail2ban
cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local
nano /etc/fail2ban/jail.local
#one week
bantime = 604800
destemail = youremail@DOMAIN.TLD
sender = fail2ban@DOMAIN.TLD
banaction = iptables-allports
#nicht postfix!
mta = sendmail
action = %(action_mwl)s
/etc/init.d/fail2ban restart
