LONDON, UK: The number of junk emails being sent globally, a major business with an estimated value of $100 billion in 2010, has reduced significantly since last Christmas, a media report said on Saturday.
The security firm Symantec said that 200 billion spam messages were sent on every single day during the summer, but during and since Christmas, it dropped to 50 billion messages per day, the Daily Telegraph reported citing the company.
Paul Wood, a senior analyst at Symantec, said: "We do see spikes and falls in the volume of spam on a daily basis but what we haven't seen before is a drop of this magnitude, which is unexpected and unexplained."
Wood told BBC News that during the Christmas period, three of the largest spam producers had cut back on their activity.
One of these botnets, the networks of infected computers responsible for circulating the majority of spam, called Rustock, dramatically cut back its activity in December.
At its peak, Rustock accounted for 47 percent to 48 percent of all spam sent globally.
However, in December, Rustock accounted for only 0.5 percent of global spam.
"There have been huge drops in spam levels before," Wood added. "Usually they have been associated with the botnets being disrupted. As far as we can tell Rustock is still intact."
Two other botnets, Lethic and Xarvester also went quiet during the same period, leading several analysts to predict that the spammers are gearing up for a larger conjoined attack across the world.
Spam accounted for 90 percent of all email sent during 2010, but most of it was filtered by email services' junk detectors. Spamming is a major business with an estimated value of $100 billion last year, the newspaper said.