When end users purge unwanted spam from their inboxes, the potential environmental impact of hitting that delete button is probably the last thing on their minds. But Santa Clara-based McAfee said the act of deleting spam and searching for legitimate e-mail contributes to green house gas (GHG) emissions equivalent to 3.1 million passenger cars using 2 billion gallons of gasoline annually.

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Or that's also 33 billion kilowatt hours annually, equivalent to the electricity used in 2.4 million homes. Whatever the illustration, spam nonetheless "has a quantifiable impact on the environment," said Dave Marcus, director of security researcher and communications for McAfee Avert Labs.

The statistics are part of a study entitled Carbon Footprint of Spam released by McAfee, based on research by climate-change researchers and spam experts.

End users' thoughts regarding spam purging is typically one of irritation, then perhaps followed by a recognition that the spam is associated with cybercrime and malware. But Marcus said the environment doesn't normally factor in the equation, especially if a single spam amounts to a mere 0.3 grams of carbon dioxide, actually "just a little puff of carbon" or like driving three feet.

"But when you look at the (yearly) volume, that is where the numbers become interesting," said Marcus, explaining that the volume of spam over a year equates to driving around the earth 1.6 million times.

Admittedly, in the grand scheme of things, that's not a tremendously large environmental impact, Marcus said, but "deleting spam and pruning their own mailboxes is where 80% of the actual spam energy utilization comes from."

The lesson is having better end user education regarding avoiding being spammed in the first place, and using better spam filter technologies for when you are spammed, because spam filtering saves electricity equivalent to taking 13 million cars off the road, said Marcus.

The environmental damage caused by spammers should have legal repercussions in much the same way that corporate entities are held responsible, said Marcus. "The green movement is very powerful and it certainly is the right thing to do," he said. "If they hold companies and corporate entities accountable for their impact on the environment, why wouldn't you hold the criminal liable for their impact on the environment?"