Re: A solution about email spam and email reliability

On Fri, 05 Jun 2009, in the Usenet newsgroup comp.os.linux.networking, in
article <h0b135$bck$1@xxxxxxxxxxxxx>, Ioannis Vranos wrote:

David Schwartz wrote:

Ioannis Vranos <ivra...@xxxxxxxxxxx> wrote:

I have thought a solution both for email spam and email reliability
problems, of Internet.

Use your favorite search engine - solutions to the problem have been
proposed for the past 15 years or more, and they are never adopted
because they all share the same problems.

1. Assuming a sen...@xxxxxxxxxxxxxx and a recei...@xxxxxxxxxxxxxxxx,
after the sender sends an email at the receiver, the
receiver.address server sends back a message with a random number
to the sender.address server.

Why should I (or any receiver) accept the mail in the first place?
Most mail from unexpected senders today is unwanted - usually spam - so
why should the receiver's mail server waste time and bandwidth on it?

3. The receiver.address server makes the email available to the
recei...@xxxxxxxxxxxxxxxxx

That is called Back-scatter - look that up in your favorite search
engine and understand why that will get the senders mail server on
a black list, or merely blocked at the receiving site.

Also most of the spam emails are sent from botnets and *not* from
real email accounts.

Then why does my mail server see thousands of ``returned'' spam that
is addressed to non-existent users at my domain - spam that was never
sent from any domain that exists within a thousand kilometers of my
mail server. Go back to that search engine, and look at the many
back-scatter block lists, or point your news reader at the Usenet
news groups

news.admin.net-abuse.blocklisting Discussion of ip-based blocklisting.
news.admin.net-abuse.email Discussion of abuse of email systems.
news.admin.net-abuse.misc Network facility abuse, including spamming.
news.admin.net-abuse.policy Discussion of net abuse policy.
news.admin.net-abuse.sightings Sightings of net abuse.

and see what others think. 'n.a.n-a.blocklisting' is an interesting
group (moderated, like n.a.n-a.policy and n.a.n-a.sightings - so you
can't just post anything), and see the whining from mail admins whose
domains/IP-ranges are listed for abuse such as back-scatter. Read the
FAQs for the groups. 'n.a.n-a.blocklisting' has existed about six
years, and there have been some 25000 articles posted to it. You ought
to read some of those before you try re-inventing the square wheel.

The free email provider I am using (www.freemail.gr), provides an
antispam option named "greylisting" which radically reduced the amount
of spam I am receiving, from many in a day to very few a week.

Blacklisting many of the "free" email providers reduces my spam load.

So in summary, my approach is based on the concept of greylisting,
and is based on the following facts:

1. 99% of spam emails are sent from botnets with fake or invalid
sender email addresses.

Prove it. But you want the victims to send mail to the address in
the spam to ask "Did you send this?" I guess another term you
should use in the search engine is "callout". See how fast that
mode of operation gets you on multiple public (and an unknown number
of private) blacklists.

2. Misconfigured legit servers may not work with greylisting (I
haven't encountered such a problem so far), and the suggested
approach *ensures* that the email ==> of only a legit email account
is received and not rejected by the recipient server.

If you are trying to send mail to me from your free email account, you
would discover that it can't even connect - never mind send anything.

I haven't understood the following of Jan Thom<E4>:

"It would also allow the spammers to check if a mailbox really exists
(by simply faking a callback message) and therefore would even promote
more spam...".

I'll bet you haven't even figured out what a "Millions CD" is. A
search engine looking for that would find stuff like:

Millions CD Vol 12 - Just Released!!

The Millions CD - VOL. 12 is comprised of over 15 MILLION PREMIUM &
SUPER clean email addresses & majority are VERIFIED!! You can start
mailing as soon as ...

Yes - you don't understand how spammers work - so you don't understand
why your plan isn't foolproof. E-mail originated back in the late
1960s, before there was an Internet. Computer accounts were rare and
not to be trifled with. As the Internet became more universal, a
few idiots realized they could make money by sending out a million
emails in the hope of finding one or two potential customers. That's
when the war against spammers began.

Old guy
.

Relevant Pages

  • Re: content filtering
    ... opinion on experience that's limited to dealing with domestic US ... Considering that the large majority of spam originates from the US, ... Now all you need is some method of identifying the sender. ... 550 code would come to the attention of the mail server admin who could ...
    (microsoft.public.exchange.admin)
  • Re: anti spam sw?
    ... It only tags suspect mail as spam. ... Bayesian filtering should ALWAYS be the *last* mechanism used to detect spam since it is a guessing scheme based on word weigthing over a historical sample set experienced by just one particular user. ... I also use the MXblocking plug-in because I don't want mails sent from dynamically IP addressed hosts. ... If someone wants to operate their own mail server then let them get a static IP address. ...
    (alt.computer.security)
  • Re: Outlook Express Undeliverable
    ... If your client is not getting an NDR message back from ... his mail server (which means his sending mail server got rejected during the ... Maybe you have server-side spam filtering enabled and his mails ... sender is infected so his mails could also be infected. ...
    (microsoft.public.internet.mail)
  • Re: How does Cron send email?
    ... Spam is invariably sent from somebody else's computer ... or through a mail server configured as an open ... Windows machine that uses your ISP e-mail server to connect to. ... have much problems with supporting the SPAM from machines they service ...
    (Debian-User)
  • Re: How to do rDNS. WAS: RE: educating rDNS violators
    ... It's done in the DNS server. ... As a spam prevention measure, a lot of end-user Internet providers are ... Using your own mail server as a slave to the ISP's mail server will add ...
    (Security-Basics)