[Sussex] Securing Mail Servers

[Ronan Chilvers]

Hi Desmond

On Sun, 16 Apr 2006 21:07:44 +0100
Desmond Armstrong <desmond.armstrong at gmail.com> wrote:

> I have a question.
> The spam that we receive does it come from improperly set up
> mailservers or/and from Windows machines which are riddled with
> trojans. One thing I am fairly certain on, it does not come from
> normal Linux boxes. What are the statistics on this point?

Lots of the spam that I block comes from dhcp assigned netblocks, so I
assume its from compromised machines on a dial up of some sort.  I do
trap some from open relays, which SPF records help to sort out.
Most of the spam I trap comes from US and Asian netblocks (the US being
the major source) and there are companies out there who happily offer
so called 'viral marketing techniques' and mass email blasts for
paying clients.  However greylisting is the most useful and effective
technique I've found for controlling incoming email, from which I
assume that the vast majority of spam does not come from 'proper' mail
servers, but rather from mass email software that operates a
fire-and-forget system.

Just FYI, message labs publish interesting stats on global spam and
virus levels that can be a little depressing.  Spam levels are running
at 66% which is better than it has been and virus intercepts at c. 2.5%.

http://www.messagelabs.co.uk/publishedcontent/publish/threat_watch_dotcom_en/threat_statistics/DA_112495.chp.html

Cheers
-- 
Ronan
e: ronan at thelittledot.com
t: 01903 739 997

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