Misguided SPAM Filtering techniques

Tue Oct 23 08:28:28 UTC 2007

On Tue, Oct 23, 2007, Dave Pooser wrote:

> It seems to me that blocking port 25 by default and unblocking on request
> would be an ideal low-maintenance solution that would reduce spam
> considerably, and has the added benefit of being on-topic for NANOG.

For those of you who run Cisco kit; you can also use WCCPv2 to
redirect 25/TCP -in hardware path without policy routing- to a farm of 
servers. Its actually documented in the WCCPv2 specification - you can
redirect arbitrary TCP/UDP ports. Think of the possibilities.
(I don't think the CRS does WCCP :P but it'll be in hardware path on
6500/7600 on anything >= SUP2/PFC2; 3560/3750/4500/4948; It'll also be
in CEF path IIRC on software platforms.)

I've done this in my lab at home and it works fine. Whats missing is
some glue to handle transparently routed connections once they hit your
SMTP farm; I'm quite happy to help people out if anyone is interested
(and I'll even put the results in the nanog wiki if people care.)

2c,

Adrian