New email monitoring data has revealed a "sudden" 30 per cent reduction in global spam volumes over the past week.
Security firm SoftScan believes that the drop is most likely to be the result of a major botnet temporarily losing control of its clients.
Another theory is that the reduction in spam might be attributed to the recent earthquake in Asia, preventing spamming activity from this region. However, this is considered to be less likely as the drop in spam distribution was not instant.
SoftScan also suggested that a large number of users received new computers at Christmas to replace infected machines, but since this trend has not been seen in previous years, it too seems unlikely.
Spam levels for December remained very high at 89.36 per cent of all email and even at their lowest point on 21 December the level was still 84.95 per cent.
"When you can easily buy kits that allow anyone to start their spam business with just a few clicks of the mouse, it is no wonder that spam levels are at breaking point," said Diego d'Ambra, chief technology officer at SoftScan.
"If spam distribution levels continue to rise at the rate we have seen over the past few months, I believe that by the end of 2007 governments worldwide will be obliged to enforce international anti-spam laws for the sake of commerce.
"It is critical that we find a way to destroy the growing army of botnets that distribute the vast majority of spam.
"Law enforcement and educating users will help, but I am not sure that it will be enough and the industry needs to work together to find a way."
Virus levels remained low in December accounting for only 0.5 per cent of all email scanned by SoftScan, despite a large outbreak of 'Tibs', the so-called Happy New Year worm, at the end of the month.
"In 2007, virus writers will continue their stance to remain undetected for as long as possible to ensure that enough machines are harvested to make it worth their while," added d'Ambra.
"The longing for notoriety is a thing of the past, and all virus writers want now is access to your computer.
"Years ago, if a machine became infected, it was such an inconvenience to the user that even if they were not aware of the threats before, they quickly took steps to prevent anything from happening again."
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