The Rustock botnet, which is responsible for a significant amount of spam messages across the globe, has somehow been shut down.
With the Rustock botnet offline, researchers have seen a significant drop in the levels of spam around the world. Rustock botnet is said to have been responsible for sending 200 billion spam messages every day in 2010.
A botnet comprises of a large number of infected computer machines that are used to send large amounts of spam emails around the world. These infected computers are controlled by a remotely located command-and-control centre.
There is speculation that security researchers were able to take down the botnet mid-operation, which is very difficult as it was thought to have almost impregnable defences. Since the apparent attack on the botnet, the command-and-control centre has been unable to reconnect with the infected computers, whose number is estimated to be in the millions.
No one knows for certain how the botnet was stopped. Phil Hay, an analyst with M86, wrote on a blog post, “It is unclear yet who or what caused the shutdown. It's also possible it has been abandoned. Over the past three years, Rustock has been responsible for a huge amount of spam, at times representing half of all spam caught in our spam traps.”