Recent rise in TLS spam, MessageLabs reports
MessageLabs Intelligence has tracked a recent rise in spam using TLS (transport layer security), a technique for sending e-mail through an encrypted channel.
In a recent report, MessageLabs noted that spam using TLS accounted for approximately 20 percent of all spam, though it rose to approximately 35 percent on a single day.
The increase in TLS spam has been accompanied by a “large increase in the volume of outbound traffic” as well because TLS also requires a “large amount of outbound traffic to negotiate encryption protocols,” said MessageLabs.
As much as 70 percent of spam from the Rustock botnet uses TLS currently, according to MessageLabs.
“Should the volume of spam from botnets that use TLS increase over the coming weeks and months,” according to MessageLabs Intelligence Senior Analyst, Paul Wood, “businesses will need to evaluate the resources needed to handle this type of spam. With corporate servers under pressure to handle these expensive but necessary TLS connections, it becomes death by a thousand cuts. The overhead of processing a single spam received with TLS alone may appear insignificant, but in large volumes the impact can become enormous.”