Subject: [Asrg] What if...

From: Andreas Saurwein <[email-masked]>
Date: Sun, 10 Aug 2003 15:24:40 -0300

Hi everybody!
I've been wondering what would happen if every mail server starts to 
blindly accept every mail address as long as it belongs to a valid domain 
served by this server. I think that is commonly known as catch-all or 
blackholes.

As I see it, this would have two effects:
1) a dramatic rise of spam sent to non-existant mail addresses
2) huge numbers of non-existant mail addresses on spammers lists

Wouldnt that render the spam lists worthless in a rather short time? Nobody 
would be able to distinguish real from wrong mail addresses anymore. 
Directory Harvest attacks would have a 100% success rate but depending on 
the program a almost 0% rate of useful results.

I am aware of the impact this might have on mail servers. But how long 
would it take for spammers change their tactics?

cheers
Andreas

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From: Yakov Shafranovich <[email-masked]>
Date: Sun, 10 Aug 2003 16:03:58 -0400

At 02:24 PM 8/10/2003, Andreas Saurwein wrote:
>Wouldnt that render the spam lists worthless in a rather short time? 
>Nobody would be able to distinguish real from wrong mail addresses 
>anymore. Directory Harvest attacks would have a 100% success rate but 
>depending on the program a almost 0% rate of useful results.
>

Assuming that a lot of spammers use someone else's computers to do the 
spamming it will not do much aside from reducing the overall spamming 
response rate but not increasing the spammer's costs since they do not 
spend money on sending the emails. Instead, it will increase the mail 
volume on the Internet thousand-fold and will make things much more 
complicated on the Internet since no one will every know whether an email 
address is valid or not. People will continue to send emails to old 
addresses thinking they are valid. Dictionary attacks are the only thing 
that this method will get rid of. At a specific point the response rate 
will fall so low that spammers will no longer have the incentive to spam. 
However, the Internet email system will probably be disrupted long before that.

The question is when will spammers stop due to the lowering response rate.. 
My suggestion would be to a setup a bunch of honeypots and see what happens.

Yakov

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From: "Menno Pieters (Stelvio)" <[email-masked]>
Date: Sun, 10 Aug 2003 22:08:00 +0200

Andreas Saurwein wrote:
> blindly accept every mail address as long as it belongs to a valid 
> domain served by this server. I think that is commonly known as 
> catch-all or blackholes.
> 

My guess is, it would take very long. It wouldn't really hurt the 
spammers. The spammers don't care that the recipients do not exist. They 
already send a lot of mail to non-existing addresses. If it gets 
bounced, who cares? Well the ISP or users whose domains or addresses are 
abused as the sender address probably do.

What would happen is that a lot of messages are simply accepted in stead 
of bounced. It gives an opportunity to feed DCC and razor networks and 
statistical filters. That's all.

Menno

-- 
Menno Pieters - Stelvio
Postbus 215, 3740 AE Baarn
phone: +31-35-5.429.324 / fax: +31-35-5.429.327
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