By Sharon Gaudin
October 3, 2007
Cybercriminals are splitting their giant botnets up into smaller pieces
to make them more agile and more easily hidden from detection, according
to a security company.
Hackers and malware writers have been diligently building up massive
botnets in recent months. Botners are a collection of compromised
computers that can be remotely controlled by the hacker. When hackers
build up an army of thousands or even millions of these zombie machines,
they can use them to send out spam, malware, and to even launch
And until just recently, they appeared to be going by the philosophy
that when it came to botnets, bigger was better. That's no longer the
case, according to Iftach Amit, director of security research at
security company Finjan.
"Smaller botnets get the job done, but smaller botnets generate a lot
less traffic," he told InformationWeek. "That makes them harder to
detect because they make much less noise. They fly under the radar when
you're looking for anomalies in behavior."
The smaller botnets also are easier to manage and easier to keep online,
He explained that many botnets are operated from a single command center
-- generally a server which the hacker uses to send out commands and
updates. If security researchers or law enforcement find that command
center, the botnet is effectively out of business. However, if the
hacker splits the botnet up into several smaller botners, each with its
own command center, if one goes down, the others remain operational.
"It comes down to financials," said Amit. "If you have a single botnet
with a single point of failure and that goes down, you lose everything.
If you cut it up into smaller botnets, you get added security."
He noted that researchers at Finjan have seen some botnets that used to
number in the hundreds of thousands broken into ones that number in the
tens of thousands.
What's not clear yet is what might be happening with the Storm worm
That zombie army has reportedly grown into a massive botnet, with
estimates ranging from hundreds of thousands to several million. The
botnet, which has pounded the Internet for the last several months with
spam and denial-of-service attacks, has become one of the largest zombie
grids researchers say they've ever seen.
Amit said it's not yet clear if the Storm worm botnet is being broken up
into smaller pieces or if it's retaining its size. The Storm botnet,
however, is not controlled by one command center, which has made it
difficult for researchers to shut it down. That also may be a reason to
not split it up into smaller pieces.
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