freebsd-src/etc/hosts.allow

#
# hosts.allow access control file for "tcp wrapped" apps.
# $Id: hosts.allow,v 1.2 1999/04/08 19:08:53 markm Exp $
#
# NOTE: The hosts.deny file is not longer used.  Instead, put both 'allow'
#       and 'deny' rules in the hosts.allow file.
# see hosts_options(5) for the format of this file.
# hosts_access(5) no longer fully applies.

# This is an example! You will need to modify it for your specific
# requirements!

# Start by allowing everything (this prevents the rest of the file
# from working, so remove it when you need protection).
# The rules here work on a "First match wins" basis.
ALL : ALL : allow

# Wrapping sshd(8) is not normally a good idea, but if you
# need to do it, here's how
#sshd : .evil.cracker.example.com : deny 

# Prevent those with no reverse DNS from connecting.
ALL : PARANOID : RFC931 20 : deny

# Allow anything from localhost
ALL : localhost : allow
ALL : my.machine.example.com : allow

# Sendmail can help protect you against spammers and relay-rapers
sendmail : localhost : allow
sendmail : .nice.guy.example.com : allow
sendmail : .evil.cracker.example.com : deny
sendmail : ALL : allow

# Portmapper is used for all RPC services; protect your NFS!
portmap : localhost : allow
portmap : .nice.guy.example.com : allow
portmap : .evil.cracker.example.com : deny
portmap : ALL : allow

# Provide a small amount of protection for ftpd
ftpd : localhost : allow
ftpd : .nice.guy.example.com : allow
ftpd : .evil.cracker.example.com : deny
ftpd : ALL : allow

# You need to be clever with finger; do _not_ backfinger!! You can easily
# start a "finger war".
fingerd : ALL \
	: spawn (echo Finger. | \
	 /usr/bin/mail -s "tcpd\: %u@%h[%a] fingered me!" root) & \
	: deny

# The rest of the daemons are protected. Backfinger and log by email.
ALL : ALL \
	: severity auth.info : spawn (/usr/bin/finger -l @%h | \
	 /usr/bin/mail -s "tcpd\: %u@%h[%a] tried to use %d  (denied)" root) & \
	: twist /bin/echo "You are not welcome to use %d from %h."