TELECOM Digest OnLine - Sorted: Re: Trial Shows How Spammers Operate

Re: Trial Shows How Spammers Operate

Scott Dorsey (
30 Nov 2004 10:58:50 -0500

T. Sean Weintz <> wrote:

> Scott Dorsey wrote:

>> In the case of the rule I gave, it will send a message to comcast's
>> abuse address whenever mail sent from a dynamically-allocated comcast
>> address arrives. There is NO REASON for anyone on a
>> dynamically-allocated block to be sending mail directly; mail sent
>> from Comcast users should go through their mail server and not from
>> their direct address. So the only mail you will ever get from these
>> blocks will be spam, mostly from zombie machines.

> Not a good idea. Some of the addresses in the Comcast dynamic IP space
> are NOT dynamic addesses, but DHCP reservations (that the customer pays
> an extra $50 per month for) -- they are not leases -- the IP address is
> reserved specifically for that users MAC address until Comcast manually
> deletes it. And such addresses have a TOS/AUP that specifically allows
> the user to run a mail server. So there IS a legit reason for some folks
> to send mail directly from a Comcast IP.

Right, these addresses are not in the same space, and they have
different rDNS. Otherwise, DNSBLs which listed all dynamic space
would be listing them as well.

Part of the problem is that ISPs don't use any uniform naming system
for addresses, so it can sometimes be a real adventure to figure out
what a given address is until you figure out their naming scheme. And
there are some out there that don't set any rDNS at all, too.


"C'est un Nagra. C'est suisse, et tres, tres precis."

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