From: Hugo Vinicius Garcia Razera (hviniciusg@gmail.com)
Date: Tue Nov 08 2005 - 12:27:28 EST
I agree whit every thing u said Tomas, but from the point off view off
a penetration testing it would be a very nice way to get what users
are valid on that domain. assuming that the only service available is
external mail for the users, witch is the case I'm working right know.
Now comes the question, if i develop such tool, and the spamers get
the hands on it i will kill my self :), i don't want no more sper.....
pills mails or... well i think u know what i mean.
An interesting way off gathering the emails(users) could be if u get a
"mailer daemon reply"
of an invalid user, so if u don't get anything, there is the
probability that the account is valid.
any comments any one.
Greetings
Hugo Vinicius Garcia Razera
On 11/7/05, Tomasz Nidecki <tonid@hakin9.org> wrote:
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> Sunday, November 6, 2005, 6:36:48 PM, Eyal wrote:
>
> > I'm not aware of any tool which can test emails against an address file.
> > The most efficient approach to achieve this functionality is to write a
> > simple script which sends the SMTP VRFY command for each entry in an address
> > file.
>
> > Note that some mail servers do not support this command in order to thwart
> > spammers.
>
> Hi, everyone.
>
> Well, to be exact, almost no servers support this command nowadays.
> qmail definitely doesn't. AFAIK, Postfix doesn't either, at least it
> didn't the last time I checked. Neither did Exim. Only Sendmail, in
> its standard config, responds to the VRFY command. I don't know about
> commercial, Windows mailservers, but I found the VRFY command
> supported in very few cases. Therefore I would not base anything on
> its output.
>
> Also, testing the existence of the user is rarely done on the level of
> mail envelope. Therefore, you cannot expect the mailserver to either
> reply right after sending the RCPT TO command that the user doesn't
> exist or reply in such away after DATA is sent. The only thing you can
> expect, is that if the user address is invalid, you will receive a
> mailer daemon reply to the MAIL FROM address.
>
> But... This is also not certain. Some mailservers use a default
> account for a given domain, eg. qmail, which I specialise in. If such
> a setup is made, all mail to inexistant users in a given domain is
> directed to a chosen existant account. Therefore you will not receive
> any answer from the mailserver, if a bad e-mail address is given in
> RCPT TO, since mail will be delivered to an existing user.
>
> Therefore, there is no tool and there will be no such tool. Which is
> good, because if there was, spammers would have a much easier life
> making databases of existing users, so they can sell them later on.
>
> Cheers,
>
> - --
> Tomasz Nidecki, Sekr. Redakcji / Managing Editor
> hakin9 magazine http://www.hakin9.org
> mailto:tonid@hakin9.org jid:tonid@tonid.net
>
> Do you know what "hacker" means?
> http://www.catb.org/~esr/faqs/hacker-howto.html
>
> Czy wiesz, co znaczy slowo "haker"?
> http://www.jtz.org.pl/Inne/hacker-howto-pl.html
>
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