Re: Trouble with Sender Authentication

On 10 Nov 2006, John Levine wrote:

> I do agree that the DNS threat from SPF is not qualitatively worse
> than what we already put up with for CNAMEs.

Actually, the top candidates for DNS amplification abuse are large SPF
records, followed by large collections IN-ADDR records for a single IP,
as is the case for large virtual hosting sites.  Both practices are
advocated by anti-spammers.

I recently saw a ~4k byte SPF record, published by an anti-spam site.  
DNSSEC signed SPF records will probably break the 8K limit.

Thats about a 90 to 1 amplification factor.

You can get some amplification with any record type.  You can only get
the high amplification with certain types and certain practices.

		--Dean



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