mailing list archives
Re: Intel.com Mailing List Arbitrary Address Removal Link
From: Todd Underwood <todd () osogrande com>
Date: Thu, 7 Feb 2002 14:00:36 -0700 (MST)
On Wed, 6 Feb 2002, Joel Maslak wrote:
The fix for this requires sophisticated bounce tracking software. The
only real way to fix this problem is to send each recipient a message with
a custom-encoded FROM envelope address, such as:
Where the user-id is some sort of database identifyer and the security key
is simply a random number kept in the database to prevent malicious
activity (it could also be some sort of cryptographic code). When the
example.com mail server receives a message to bounce-xxx-yyy () example com,
it checks the security key, verifies that the bounce is a permanent
bounce, and deletes the user.
it's worth noting that this is a succinct description of VERP (variable
envelope return path), something used by ezmlm and qmail to accomplish
exactly this--make it difficult to forge a bounce and easy to determine
true per-recipient bounces. VERP makes handling large mailing lists
trivial and significantly reduces this security problem.
see http://www.lifewithqmail.org/lwq.html#verp for a good description.
todd underwood, vp & cto
oso grande technologies, inc.
todd () osogrande com
"Those who give up essential liberties for temporary safety deserve
neither liberty nor safety." - Benjamin Franklin