add this:
[asterisk-iptables]
# if more than 4 attempts are made within 6 hours, ban for 24 hours
enabled = true
filter = asterisk
action = iptables-allports[name=ASTERISK, protocol=all]
sendmail[name=ASTERISK, dest=you@yourmail.co.uk, sender=fail2ban@local.local]
logpath = /var/log/asterisk/messages
maxretry = 4
findtime = 21600
bantime = 86400
to the end of of jail.conf? per:
http://www.fail2ban.org/wiki/index.php/Asterisk
I saw a [general] tab so modified that as directed, but didn’t see [asterisk-iptables] … so added that section.
Asterisk 13.1.0~dfsg-1.1ubuntu4