Product SiteDocumentation Site Expansions
Expansions, when used in conjunction with the spawn and twist directives, provide information about the client, server, and processes involved.
The following is a list of supported expansions:
The following sample rule uses an expansion in conjunction with the spawn command to identify the client host in a customized log file.
When connections to the SSH daemon (sshd) are attempted from a host in the domain, execute the echo command to log the attempt, including the client hostname (by using the %h expansion), to a special file:
sshd :  \
	: spawn /bin/echo `/bin/date` access denied to %h>>/var/log/sshd.log \
	: deny
Similarly, expansions can be used to personalize messages back to the client. In the following example, clients attempting to access FTP services from the domain are informed that they have been banned from the server:
vsftpd : \
: twist /bin/echo "421 %h has been banned from this server!"
For a full explanation of available expansions, as well as additional access control options, refer to section 5 of the man pages for hosts_access (man 5 hosts_access) and the man page for hosts_options.
Refer to Section 2.5.5, “Additional Resources” for more information about TCP Wrappers.