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Re: What would happen to Challenge/Response if ...



On Thu, Oct 23, 2003 at 12:53:49AM -0700, Steve C. Lamb said
> On Thu, Oct 23, 2003 at 05:32:59PM +1000, Rob Weir wrote:
> > Hm, now I check, 27253 of those did *not* come from my secondary MXs.
> > That is a stupid amount of crap.  In fact, it is 3.8985GB of crap.
> > Imagine that instead of dropping that shit on the floor, you sent a CR
> > query.  You've just doubled the number of mails flying around (thought
> > not the volume, of course).
> 
>     Ya forgot to mention that of those 27253 messages (just using your count
> as an example) damn nead close to 0 are likely to reach an infected host since
> SWEN spoofs and lots of C-R systems fall for it.

Ah, yes, that's even worse.  I'm also bloody sick of getting "a virus was
detected in your mail" messages from people I have never written to.

>     BTW, just curious how you detect SWEN before the MTA gets it?  Usually
> mine is post-contact on at least one occasion.  After that it was firewall but
> now it is just drop on a RCPT test.  Hrm, should make it a HELO test.  :/

I'm dropping mail based on a DATA regexp.  I have the following line in /etc/postfix/ms-crap

/^TVqQAAMAAAAEAAAA\/\/8AALgAAAAAAAAAQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA$/   REJECT Message rejected, contains the Swen worm virus!

and this line in /etc/postfix/main.cf to make use of it

body_checks = regexp:/etc/postfix/ms-crap

No doubt any other servicable MTA can handle it.  Oh, and to get my counts, I use 

grep Swen /var/log/mail.log|awk '{print $6}'|sort|uniq|wc -l

Add a grep -v for your secondary MX's before the awk to filter non-direct
attempts.

-- 
Rob Weir <rweir@ertius.org> | mlspam@ertius.org  |  Do I look like I want a CC?
Words of the day:        ASLET USCODE Crowell Mantis Maple illuminati kilderkin

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