[LINK] Spam filter eliminates 99% of junk mail
ivan at itrundle.com
Fri Nov 16 16:35:12 AEDT 2007
On 16/11/2007, at 11:04 AM, Tom Worthington wrote:
> I did a quick check to see if my SpamAssassin Spam filter was
> working. The result was that the filter is catching 99% of the Spam,
> which makes up 96% of the email I receive. No messages were
> incorrectly classified as Spam.
Interesting data, Tom - it confirms that my system is not that
unusual, nor special.
> I then looked through the remaining 32 messages not rated as Spam by
> the system. Of these, seven I considered to be Spam.
> The Spam filter appears to be working very well. I could make it
> more sensitive, but seven junk messages a day is acceptable.
I use DSPAM (from Jonathan Zdziarski, though he has sold the rights
recently, I gather), and it tells me that it has been 99.759% accurate
in the past 12 months.
91.393% of my mail is spam: an average day lately indicates that I
receive about 950 messages as spam. No good messages have been
classified as spam for a very long time (12 months or more), and spam
that makes it through to my pop server averages about 2 or 3 per week
The settings that I use are the average settings, and I have not had
any need to make them more or less sensitive, though I do enable
'noise reduction', and have it automatically whitelist frequent
correspondents. I have an additional spam filter on my mail
application, and it successfully identifies the strays. In all, the
combination of DSPAM and Apple Mail app's junk mail filter capture
100% of my spam.
I have noted a large increase in spam in the past month - my daily
average of spam caught by DSPAM usually hovers around the 600-700
messages per day. And although I've attempted in the past to
reconfigure my mail server to authenticate mail prior to arrival,
there are too many government departmental mail systems that I deal
with which then get blocked. DSPAM adds around 0.416 seconds
processing time to each message, and offers many other stats on
everything from inoculations, auto-whitelistings, spam/non-spam, spam
misses and false positives.
Colleagues who have used or continue to use DSPAM have varying results
(I manage their domains to a grater degree) - in particular, those who
like to receive a lot of automated messages heavily laden with non-
plain text seem to suffer the most (their accuracy fluctuates between
90% to 98%).
Of course, 99.9% accuracy is all well and good if the spam levels are
low, since the final messages that get through are the ones that get
in the way. I'm happy that I rarely see spam these days, and the
diligence in training DSPAM has thoroughly paid off.
I don't bother with virus protection, as I have no need of it at the
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