[kwlug-disc] clearing close_wait

Fernando Duran liberosec at yahoo.ca
Thu Mar 24 22:04:29 EDT 2011


----- Original Message ----
> From: John Van Ostrand <john at netdirect.ca>
> To: KWLUG discussion <kwlug-disc at kwlug.org>
> Sent: Thu, March 24, 2011 8:39:45 PM
> Subject: Re: [kwlug-disc] clearing close_wait
> 
> ----- Original Message -----
> > Not related to CLOSE_WAIT but to prevent  this issue of an IP opening a
> > lot of
> > connections you can setup  the proper parameter in your mail server
> > (for example for  Postfix
> > http://www.postfix.org/postconf.5.html#smtpd_client_connection_count_limit
> >  )
> > , xinited also can limit the number of simultaneous client
> >  connections. Or directly from iptables using
> > connlimit: http://www.cyberciti.biz/faq/iptables-connection-limits-howto/
> 
> Good  direction Fernando.
> 
> It's also a good idea to do a greeting delay. This  works well for us. The idea 
>is that your MTA accepts connections and if the  remote IP is not on your 
>network or localhost it enforces a 15 second delay  before issuing the first 220 
>message. Spam daemons don't wait for that and start  the SMTP conversation. When 
>the MTA sees traffic before issuing the 220 it  rejects all commands for the 
>session.

Yes, definitively.

For spam what has worked for me lately is the similar idea of greylisting 
(apt-get install postgrey) and configuring in Postfix the blacklists (like 
spamhaus and spamcop); spamassassin doesn't work well (spam is processed 
anyways) and consumes a lot of CPU. But what I tell people asking me now about 
mail servers is just go to gmail / google apps if they accept the possible 
privacy issues and save the trouble.


 ---------------------
Fernando Duran
http://www.fduran.com


> 
> -- 
> John Van Ostrand 
> CTO,  co-CEO 
> Net Direct Inc. 
> 564 Weber St. N. Unit 12, Waterloo, ON N2L 5C6 
> Ph: 866-883-1172 x5102 
> Fx: 519-883-8533 
> 
> Linux Solutions / IBM  Hardware 
> 
> 
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