DOS attack using RSET commands?

[Martin Hepworth]

Travis

Seeing a lot of these I wasn't seeing before... (in Exim)

SMTP protocol violation: synchronization error (input sent without waiting
for greeting): rejected connection

about 25% of my reject log is this rubbish, don't recall seeing this before.

And I only reject on unknown user for that connection..I don't use any
access list on the MTA.

--
Martin Hepworth 
Snr Systems Administrator
Solid State Logic
Tel: +44 (0)1865 842300

> -----Original Message-----
> From: mailscanner-bounces at lists.mailscanner.info [mailto:mailscanner-
> bounces at lists.mailscanner.info] On Behalf Of Travis Taylor
> Sent: 23 June 2006 13:00
> To: mailscanner at lists.mailscanner.info
> Subject: OT: DOS attack using RSET commands?
> 
> Apologies about multiple posts, but appears my postings are not making
> it to the mailing list.
> 
> Anyone else noticing a large surge in number of clients/connections
> issuing repetitive RSET commands when the connection is permanently or
> temporarily rejected?
> 
> The majority of the connections appear to originate from the RIPE and
> APNIC netspace.  It is getting to the point where the load is 3 times
> normal and email delivery to us is extremely slow due to the large
> number of repetitive open connections.  Anyone have similar issues?
> 
> --
> Travis Taylor
> Unified School District 373
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