Spam in the form of email has seen a drastic decline in the last few months. One report shows a fall from 200 billion spam messages being sent each day in August to only 50 billion per day in December. It’s difficult to say exactly why this has happened, but there are several theories.

Inactive botnets

Botnets are networks of infected computers which account for the majority of the world’s spam. Just one of the botnets, Rustock, was responsible for nearly 50% of all global spam at its peak. Rustock, along with two of the other prominent botnets stopped churning out so much spam in December.

Usually, botnets stop spamming because they have been temporarily disturbed, but that doesn’t seem to be the case with Rustock. The most practical explanation is simply that the people controlling Rustock decided to stop spamming as much.

Anti-spam campaigns

Spammers are primarily driven by profit. When they stop seeing profit as a result of their work, they are likely to give up and move on to something else.

Recent anti-spam campaigns have been successful in disrupting spammers’ efforts therefore decreasing their profitability. This could be a reason for their halted efforts.

Other outlets

One very plausible explanation could be that spam isn’t declining so much as it is just being transferred to other forms of media. Twitter and Facebook, for example, have recently become huge outlets for spam.

These are all logical theories behind the decline of email spam. However, nobody can be certain as to what specifically is causing it. For more information on the topic, check out this BBC News article.