Port 25 filters - how many here deploy them bidirectionally?

John Levine johnl at iecc.com
Sun Jan 9 17:20:10 UTC 2005

>Please consider the situation of net abuse with the source address
>being an infected PCs on a dialup pool that has port 25 filtering
> [ triangular routing ]

Back when Ernesto Haberli was active, this was his trademark
technique.  He'd burn through large numbers of dialup accounts, but
hide the address of his high-speed connection.

At the time he left the business a few years ago it worked pretty well
and I gather he left because he'd run out of high speed ISPs to sign
up with.  I'd be interested to know if triangular routing is used by
particular people now, or is it just another trick thrown into the mix
along with zombie proxies and such.

John Levine, johnl at taugh.com, Taughannock Networks, Trumansburg NY

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