[Techtalk] Re: filtering spam with spamassassin

[Carla Schroder]

On Thursday 11 September 2003 9:03 pm, showercurtain wrote:
> On Wed, 10 Sep 2003, Carla Schroder wrote:
>
> >All other DNSRBLs are free, and superior to MAPS. DNSRBLs are great
> >for heading off garbage before it ever hits your servers.
>
> That's basically what my organisation wants to do, although I suspect
> some people think that's going to stop spam completely. Why did you
> find other rbls better than MAPS?

Feh, there is no way to stop it completely. The best you can hope for is a 
balance between letting some through to minimize losses on legitimate mail. I 
don't know where people get these ideas- the Internet is not like cable TV, 
where you can block certain channels. Spam does not come all neatly labeled 
for easy filtering. Spammer are loathesome criminals who steal bandwidth and 
shift the cost of their spew to the receiver. They exploit poorly secured 
proxies and relays. They steal ISP accounts. They employ viruses to capture 
poorly-secured Windows boxes (redundant, I know) to turn them into 
spam-spewing zombies. Spammers pull every trick in the book to evade filters 
and blocklists.

There is absolutely no stopping it completely. Apologies for the rant, but I 
have this conversation with customers every week.  :)

MAPS is weak. They cave in to spammers who object to being listed. Their 
criteria for listing are weak. It is difficult to get on the MAPS RBL, and 
easy to get off. And they have the nerve to charge money. I hope none of your 
people think $$ is superior to free. 

>
> Another problem is configuring postfix to use an rbl database. Will
> this cause any disruptions with sending and receiving mail?

No, because it works at the DNS level it is very fast. The blocked messages 
never hit your server at all. These links might be helpful:

Realtime Black-hole Lists: Heroic Spam Fighters or Crazed Vigilantes?
http://networking.earthweb.com/netsysm/article.php/1594561

Spamfaq
http://www.spamfaq.net/

I'll answer your other questions after reviewing my notes.

-- 
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Carla Schroder
www.tuxcomputing.com
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