Rustock is not the only botnet that has stopped operations. The Harnig botnet, also known as Piptea, also went offline at about the same time. But the command and control servers apparently are still lurking on the Web, ready to be used again by bot herders.
Shutting
down the Rustock botnet in early March appears to have had an unexpected side
benefit: the Harnig botnet apparently has ceased operations.
On the
very day that law enforcement authorities, with Microsoft's help, were raiding Rustock's command-and-control servers, the servers belonging
to the Harnig botnet-also known as Piptea-stopped responding, according to
Atif Mushtaq, a security research engineer at FireEye. Rustock used to be
spread by Harnig, suggesting some kind of a relationship between the two
botnets, Mustaq wrote on the company's Malware Intelligence Lab March 22.
It was rare to see Rustock using some other infection
vector or network to propagate, according to Mushtaq. Microsoft's Digital Crime Unit estimated there were about a
million Rustock zombies.
"Keeping in view the timing of this sudden shutdown
and Harnig's obvious relationship with Rustock, it can't be a coincidence,"
Mushtaq said.
The stopped activity doesn't really mean much, as the
command-and-control servers have not been taken down and are likely to be still
under the botnet owners' control. The servers have been wiped clean of any
traces that could give away their identity or location to law enforcement. The
infected computers making up the botnet army remains infected, as well.
"It looks like a decision made solely by the bot herders,"
Mushtaq said.
Just as
the Harnig zombies remain infected, so are the Rustock zombies. Even with the
command-and-control servers gone, the infected machines are still out there,
meaning the Rustock gang, which is still at large, can set up operations again.
There is a "great chance" that Harnig will soon resume its activities, and
Mushtaq wondered if the botnet would drop new Rustock instances to revive the
botnet.
Knocking
out Rustock had some impact on global spam volumes immediately after the raid,
even though the monthly MessageLabs report for March indicated that overall volume
decreased a measly 2 percent. Even though Rustock at one point had accounted
for nearly half of all spam being sent, its absence is not as obvious because
other botnets, namely Bagle, have increased their output to fill the void left
behind.
Even so,
Harnig being out of commission may have a "significant impact on worldwide
malware infection levels," said Mushtaq. Like Rustock, Harnig also does not
appear on Damballa's latest top 10 list of largest botnets. Infecting
computers in North
America.
Dismantling Harnig would be a more difficult task than
Rustock was, since Harnig's command-and-control servers are scattered all over
the world and not just based in the United
States, Mushtaq said. According to FireEye
analysis, about 45 percent of the servers were in Russia
and 26 percent in the United States,
but they also had a presence in China,
Japan, Italy,
India, Brazil,
Germany, Poland
and Latvia. He
considered it "amazing" that even though most of the servers appeared to be
hosted in safe havens, the herders still chose to suspend, even if it's only
temporarily, all malicious activity.
Even
though there was no immediate danger to Harnig as no one was really going after
it, the Harnig bot herders panicked and felt they better go underground for a
while, Mushtaq speculated.
"The
Harnig and Rustock operators must have been very close to each other," he said.
Mushtaq
didn't rule out the possibility that the same gang ran both Rustock and Harnig.
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