Spam in the form of email has seen a radical 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.
Botnets are simply networks of infected computers that account for the vast majority of global spam. Just one botnet, known as Rustock, accounted for nearly 50% of the world’s spam at its peak. Rustock, along with 2 other major botnets saw a huge decrease in activity at the end of 2010.
Normally, when a decline so significant occurs, it is due to a disruption in the network, which is fairly easy to repair. In Rustock’s case, there seems to have been no disruption. So, the people who run the network must have just chosen to stop spamming, for whatever reason.
Spammers like to see profit as the primary result of their efforts. When their profits start to decline, their motivation seems to disappear.
It seems that a number of recent anti-spam campaigns have caused several spammers to lose profitability and shut down. One of the biggest spammers, Spamit, closed in September due to increased attention caused by these campaigns.
Twitter and Facebook have become huge outlets for spammers, which could be one explanation for the decline of traditional spam in the form of email. Social media networks generally spread spam quickly, making them ideal for spammers.
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.