Mike Clarke/AFP/Getty Images
A computer screen inbox displaying spam.
A computer screen inbox displaying spam. Mike Clarke/AFP/Getty Images
Over the past four months, the amount of e-mail spam sent globally has plummeted. The security company Symantec, which has kept track of spam volume since 2002, estimates that last summer about 200 billion pieces of spam were sent a day, yet by Christmas the number had dropped to 50 billion per day.
The BBC spoke to Paul Wood, a senior analyst at Symantec Hosted Services, who said three of the largest spam producers or botnets went inexplicably quiet. They explain:
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.
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.
Wood's colleague Mathew Nisbet, a malware data analyst, wrote in a blog post that this lull is no reason to celebrate:
Whilst this is an excellent gift over the holiday season for anyone who regularly uses email, we would not expect the level of spam to stay this low for long. As we saw after the closure of McColo in 2008, and following futher takedown attempts in subsequent years, botnets rarely stay quiet for very long. Even if these three botnets don't come back soon, we would expect other botnets, even new ones, to pick-up where they have left off - very soon.
According to Symantec's numbers, the last time the level of spam was this low was in mid-2007.