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But, while most products have good overall catch rates, the
report also found that they have a significantly harder time
with spam sent from web hosts: such spam emails are more than
three times as likely to make it past a filter than other kinds
of spam.

"A lot of the focus in the anti-spam industry has been on
botnets of compromised home PCs," said VB’s Anti-Spam Test
Director, Martijn Grooten. "And while these botnets still send
a lot of spam, spam filters have become quite good at dealing
with it."

Grooten continued: "Various recent reports have suggested that
spam is increasingly being sent from web hosts - many of which
are compromised. Our results show that this isn’t merely a shift
in the way in which spam is sent, but it actually increases the
likelihood of the spam messages making it to someone’s inbox."

"Indeed, the report shows that well over 1% of spam sent from
web hosts manages to bypass spam filters, compared with less
than 0.3% for spam sent via other means. Of course, 1% still
means the vast majority of messages are blocked, but with spam
campaigns easily running to millions of emails, this difference
can make or break the campaign for the spammer."

The VBSpam quadrant plots products’ spam catch rate against
their false positive rate, with the top right-hand corner the
area products should be aiming for (with maximum spam catch rate
and minimum false positive rate). The front-runners in this test
can clearly be seen from their positions on the quadrant at
http://www.virusbtn.com/vbspam/charts/vbspam-chart-0513-1200.jpg
(journalists are permitted to reproduce this chart unedited).

The results of the May 2013 anti-spam comparative review can be
seen at http://www.virusbtn.com/vbspam/archive/test?id=187

The full review, including detailed results tables and analysis,
is available to Virus Bulletin subscribers or can be purchased
as a standalone review ($19.95) from
http://www.virusbtn.com/vbspam/archive/list