ISP wants to stop outgoing web based spam

Fri Aug 11 16:02:26 UTC 2006

> On 10 Aug 2006, at 22:07, Barry Shein wrote:
> [...]
> >The vector for these has been almost purely Microsoft Windows.
> 
> I wonder. From the point of view of a MX host (as opposed to a  
> customer-facing smarthost), would TCP fingerprinting to identify the  
> OS and apply a weighting to the spam score be a viable technique?

We have been doing that in our traffic shaping SMTP transport for a
while now. We have found a 95% correlation between spam sources and
Windows hosts. If you drill down to specific versions of Windows, the
correlation is even higher.

For _blocking_ connections (as opposed to, say, just slowing them
down), you must combine host type with reputation information.

Regards,
Ken

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