[ISN] Rustock botnet ditches encryption to ramp spam

From: InfoSec News <alerts_at_private>
Date: Wed, 25 Aug 2010 00:37:10 -0500 (CDT)
http://news.techworld.com/security/3236787/rustock-botnet-ditches-encryption-to-ramp-spam/

By John E Dunn
Techworld
24 August 2010

The Rustock mega-botnet appears to have ditched the experimental use of 
TLS (transport layer security) to obscure its activity, Symantec has 
reported.

Rustock’s use of TLS is now averages between 0.1 and 0.2 percent of all 
spam, peaking at 0.5 percent, a tiny fraction of the levels seen in 
March when it reached averages of around 25 percent with a peak of as 
much as 77 percent.

The key moment was on 20 April, when the volume of spam featuring the 
tactic suddenly plunged to sub-one percent levels after an equally 
sudden rise in rates in the weeks prior to that date.

TLS adds a small but cumulative overhead to server email processing, 
which ties up mail servers but also affects the rate at which spam is 
sent. Why Rustock’s controllers adopted the technique at all was never 
clear but might have been connected to a misplaced belief that it would 
make it harder for servers to filters its activity or detect the command 
and control system used to direct its activity.

[...]


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Received on Tue Aug 24 2010 - 22:37:10 PDT

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