[Esd-l] spam / From address verifier

John D. Hardin jhardin at impsec.org
Mon Aug 5 06:44:01 PDT 2002

On Mon, 5 Aug 2002, Peter Warasin wrote:

> > Bear in mind the overhead of a response mail attempt on every inbound
> > message. You probably only want to do this if the message fails a
> > whitelist check.
> hm.. yes.. the mailserver is also a target for dos-attacks if the script
> is runnig. if someone is sending mails with an emailadress of an
> inexistent domain and the mailserver let it pass, or if the lookup for
> mx-hosts results an inexistent host, the script must wait for the
> dns-timeout. 
> i think thats the greater problem but i have no chance to solve this. :(

Spammers regularly send long lists of sequentially or randomly
generated email addresses in the hopes of getting a "hit". Fortunately
they don't actually try to generate an email, so they wouldn't DoS you
by doing this.

 John Hardin KA7OHZ    ICQ#15735746    http://www.impsec.org/~jhardin/
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