Re: Port 25 filters - how many here deploy them bidirectionally?

On Sun, 9 Jan 2005, Suresh Ramasubramanian wrote:

Applying port 25 filters both ways (inbound and outbound to your dialup pool, instead of just outbound port 25 filtering) would help in such a situation.

It's good to clarify that this "bidirectional" filtering does not mean filtering inbound to port 25 on the dialup box, but rather filtering inbound *FROM* port 25 to the dialup box on any port (after all, you want to block the 3WHS SYNACK and the subsequent in-stream ACKs). This is a common, but critical, mistake. -- -- Todd Vierling <tv@duh.org> <tv@pobox.com>