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Here's some snippets from a Google search:

  • Report: Spam now 90 percent of all e-mail
  • 4% of all internet traffic either DDOS packets or spam email
  • more than 50% of email is SPAM
  • Spam traffic dropped precipitously in January, falling to 78.6 percent of all emails

Is there a reliable source to identify the amount of total internet traffic that is spam emails?

How is this calculated?

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I am in a low boil over the criminal naivete' of the internet founders, who seemed to think it would be so wonderful as to be used only for high-minded purposes. How simple it would have been for email to have a concept of postage, and how simple to have senders who couldn't hide. – Mike Dunlavey Apr 15 '11 at 11:13
@Mike Dunlavey I see that you are one of the lucky ones who doesn't have it's mailbox full of publicity twice or three times a week. And it is really easy to send letters without any return address. One of the beauty of the net is the fact that is is based on a "Thrust" network, allowing it to be incredibly resilient to disruption. This is also one of its biggest weakness but it can arranged with appropriate encryption/certificates (Of courses classes on security should be given in high school instead of Word/Excel...) – Zenon Apr 15 '11 at 12:03
up vote 7 down vote accepted

Some of these statistics seem to be widely used. Due to several botnet takedowns by Microsoft along with law enforcement agencies, reduce spam amounts drastically for a few weeks but they seem to creep up again. (This article for example says Global spam 88% of emails, but spam fell by a third after the Rustock botnet takedown by Microsoft. The source seems to be MessageLabs, an anti-spam brand of Symantec. They use statistics from servers running their software.)

Another good source seems to be MAAWG, which use confidential data from ISPs, mail providers etc. to collect statistics on about 500 million mailboxes. They estimate spam from between 88 to 91 percent of email traffic.

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I agree. Also, I heard once a talk from an CEO of an Irish email provider, where he stated that they refuse about 80-90% of all incoming emails early during the connection phase between the source and their email servers. This was because spam bots often did not implement the full email exchange protocol correctly and could be detected this way. So these spam emails wouldn't even go into the mailbox, reducing the CPU power required testing their content for spam keywords. – Martin Scharrer Apr 11 '12 at 17:19

MessageLabs and other Security-as-a-service providers are in an excellent position to provide these statistics. They all agree that in recent years the number has been above 80% almost continuously. Every spam botnet takedown temporarily reduces spam, however numbers rapidly increase as other spammers move in — see this article at The Register.

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