Symantec’s June 2015 Intelligence Report includes some eye-catching numbers, and predictably generated a lot of quick press coverage. But how reliable is that figure? Unfortunately the publicly-available report is light on details and methodology, and doesn’t provide message volumes. Do other sources agree with their assessment?Symantec claims that the “overall spam rate” has dropped to 49.7% of the mail traffic they analyzed in June 2015. They don’t provide volume numbers, and only compare the figure with 2003. But it’s interesting to contrast this figure with their 2009 reports that put spam levels over 90% as reflected in their June 2009 Spam and Phishing blog post, or their August 2009 State of Spam report.

While Symantec didn’t include volume data, an article at VentureBeat suggested they had obtained the figures of 704 billion messages overall, of which 353 billion were spam, from Symantec. Obviously these numbers have been rounded off, but even so that appears to indicate a spam rate of 50.1% — if VB reversed the spam/not-spam numbers, the level would appear to be 49.87%… Perhaps 0.17% is small enough difference to overlook, though at these volumes that’s over a billion messages!

Could the 353 billion figure be a daily volume? It seems unlikely as that would reflect a June volume of over 10 trillion messages – a hefty increase over the monthly volumes they reported for 2009.

What about other sources? Kaspersky’s Securelist reported that spam in Q1 2015 was 59.2% of all observed email, and had dropped 6 percentage points from the previous quarter. That would seem to offer some support for the Symantec figure, but there were no volume figures and the percentage covering June wasn’t available yet.

TrendMicro’sĀ Global Spam Map offers a world-wide spam volume projection based on messages they observe, but it doesn’t offer a figure for spam as a percentage of all email traffic. However their volume of roughly 1.847 billion spam messages for June is only twice what VentureBeat attributes to Symantec…

Cisco’s Senderbase, by contrast, reports spam levels as holding steady at roughly 86% for the past month, the past six months, and indeed for the past 18 months. Furthermore they claim a daily average spam volume in June 2015 of 187.77, or 5.633 trillion messages – quite at odds with the VentureBeat/Symantec figure of 353 billion for the entire month. The most recent Cisco Annual Security Report puts the daily volume of spam for November 2014 at 259 billion, or 7.77 trillion for that month.

I was surprised to find there weren’t that many sources claiming to offer global spam volumes. Proofpoint, for example, only offers a breakdown of what lands in it’s honeypot network for June, though they reported a 54% year-over-year decline in spam volume – not as a percentage of received email – for February 2015.

In the end there are more questions than answers after this cursory investigation. Apparently we’ll just have to wait for more details from Symantec, or hope that other researchers to offer their own figures.