Rustock botnet sends 39 percent of all spam

Botnets are now responsible for sending 95 percent of all spam, up from 84 percent in April, and almost half of that spam comes from a single botnet, Rustock.

Rustock sent 41 percent of the world's botnet spam in August, up from 32 percent in April. This is despite the network actually shrinking in size from 2.5 million to 1.3 million bots over the same period, security company Symantec said on Tuesday. This means Rustock is currently responsible for 39 percent of all the world's spam emails.

The reason for the rise in spam from the botnet is that it has stopped using transport layer security (TLS) encryption, Wood said. By foregoing TLS encryption, Symantec believes, Rustock has been able speed up the rate at which it can send spam email, because it longer takes a performance hit from encrypting messages.

For more of this story, read Rustock botnet responsible for 39 percent of all spam on ZDNet UK.