blocking telnet to selected IPs?

[Peter Murray]

--On Sun, Jul 12, 1998 4:12 PM -0400 "Vladislav S. Davidzon"
<davidzon at metronet.lib.mi.us> wrote: 

> I am not sure if you can block sendmail via TCPWrappers, as sendmail
> usually runs as its own process, not via inetd.  I've never seen sendmail
> filtered out via tcpd [tcpwrappers], HOWEVER sendmail can be configured
> not to accept connections from certain hosts.

I may have read too much into the original message, but I assumed the author
wanted to prevent telnet access to a multi-user machine of some sort where
people were accessing mail.  In that case, TCP Wrappers installed on the
telnet port of the e-mail machine would prevent access from OPAC machines.

It is possible to use TCP Wrappers to filter SMTP connections, but since it
involves forking another process for each incoming mail message rather than
running sendmail as a daemon, it is usually not seen as an efficent way of
blocking connections.  I believe later versions of sendmail have facilities
for doing this if blocking SMTP connections from particular machines is the
original goal:

  http://www.sendmail.org/antispam.html#RefuseMail


Peter
--
Peter Murray, Library Systems Manager                    pem at po.cwru.edu
Digital Media Services                 http://www.cwru.edu/home/pem.html
Case Western Reserve University, Cleveland, Ohio          W:216-368-5888