SMTP spoofing ?
Jon Lewis
jlewis at inorganic5.fdt.net
Thu Feb 19 18:00:10 UTC 1998
On Thu, 19 Feb 1998, Perry E. Metzger wrote:
> John R Levine writes:
> > Are there any routers currently available that can do port 25 spoofing for
> > dialup users? That is, when the user attempts to connect to port 25
> > anywhere, he in fact connects to port 25 on your own SMTP server instead.
> >
> > In case it's not obvious, it's for spam management.
>
> It seems simple enough to block all outgoing SMTP to anything but your
> own server, and to apply such a filter on your dialups. I don't know
> if the more complex solution you propose is worth it -- the users will
Couldn't this be done with transparent proxy just as some ISP's do it for
web proxying/caching?
CONFIG_IP_TRANSPARENT_PROXY
This enables your Linux firewall to transparently redirect any
network traffic originating from the local network and destined
for a remote host to a local server, called a "transparent proxy
server". This makes the local computers think they are talking to
the remote end, while in fact they are connected to the local
proxy. Redirection is activated by defining special input firewall
rules (using the ipfwadm utility) and/or by doing an appropriate
bind() system call.
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