Global spam e-mail levels suddenly fall The amount of junk e-mail being sent across the globe has seen a dramatic fall in recent months.
The volume of spam has dropped steadily since August, but the Christmas period saw a precipitous decline.
One security firm detected around 200 billion spam messages being sent each day in August, but just 50 billion in December.
While the reasons for the decline are not fully understood, spam watchers warn the lull may not last.
Around the Christmas holidays, three of the largest spam producers curtailed their activity, Paul Wood, a senior analyst at Symantec Hosted Solutions told BBC News.
"But it's hard to say why," he added.
The vast majority of spam is sent by networks of infected computers known as botnets.
One of these botnets, known as Rustock, was at its peak responsible for between 47% to 48% of all spam sent globally, said Mr Wood.
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We've yet to see any evidence that spam has become a bad business to be in”
End Quote Paul Wood
In December, Rustock was responsible for just 0.5% of global spam, he said.
At the same time, two other prominent spamming botnets, Lethic and Xarvester, also went quiet.
There have been huge drops in spam levels before, said Mr Wood.
"Usually they have been associated with the botnets being disrupted. As far as we can tell Rustock is still intact," he added.
That means those controlling Rustock could have continued churning out masses of spam, but for whatever reason, have chosen not to.