David MacQuigg wrote:
At 10:49 AM 2/2/2008 +0100, Alessandro Vesely wrote:
If the original sender provides no signature, it is difficult to
discover that a trusted forwarder has become a spammer. We should
devise a technique for detecting if a message has not actually been
forwarded. Checking a random sample may suffice. Any idea?
Seems to me that once a forwarding relationship has been properly
established between two Agents, the only responsibility of the
downstream Agent is to not allow forgery of a specific connection (
Forwarder ID, RCPT Address ). If the authorized Forwarder itself is
bad, the Recipient must take action.
So you're basically saying that it's up to recipients to delete any
forwarding that starts delivering just spam. Probably that's better than
any complicated cross checking that might be devised. Checking that the
deletion of a forwarding is being honored is one stringent test that can
be carried out to maintain a forwarder's trustworthiness.
In addition, a forwarder may reserve a different name (or IP) for
forwarding messages signed by some previous hop, thereby allowing the
"MDA" to check them while the forwarding relationship is operative. Such
possibility may or may not be relevant or not for the downstream agent.
|-------- Recipient's Network ---------|
/
--> / --> Receiver/Forwarder ~~> MDA ==> Recipient
/
Border
If the downstream Agent does not accept this responsibility (my MDA
does not), the same result can be achieved by just keeping your mailbox
address secret. My MDA address has a few random digits known only to
my Forwarders. It has been operating for months with no problem.
I know what you mean. However, that only works for a particular setup.
Even in your case, a good FF implementation might provide the added
functionality of a centralized forwarders management, seamlessly
integrating forwarders and mailing lists, irrespective of the number of
hops they are far from the final recipient.
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