[Mimedefang] Dictionary attacks, NDRs etc..

[WBrown at e1b.org]

mimedefang-bounces at lists.roaringpenguin.com wrote on 12/05/2003 12:24:30 
PM:

> 
> I admit I have not read the RFC dealing with the above but,
> in the above we are telling the spammer which addresses are good
> and which are bad?
> 
> This is a serious security breach. If I was a spammer I could write 
> a program to mine all good addresses using the same process.
> 
> Would it not be better to do the LDAP lookup and simply remove
> the recipient in @Recipients and not give the spammer any idea
> which addresses are good or bad?
> 
> It may violate an RFC but aren't we in a "War against SPAM"?
> Maybe the RFC needs to be re-written. SPAM was not an issue
> then like it is now I would think.

Adelphia does not return delivery failures for addresses that are invalid, 
including no longer used addresses.  If ham is not delivered, it should 
generate an NDR. 

I am just starting on implementation, but I anticipate returning perm 
failures on spam.  The trick is detecting the dictionary harvest attack 
and blocking that server from further connections.