Spammers have been hard at work at regaining their past momentum. Over the past year, the botnet landscape has changed, especially since the McColo shutdown.
It's been roughly two months since the much-heralded shutdown of McColo
, yet spam levels have remained below where they were previously.
While the amount of spam hitting
enterprise networks is building as botnet operators regain their momentum, the botnet landscape
changed significantly. Some of the former kings of the hill, botnets
such as Srizbi, were badly hurt by the shutdown.
In its place, botnets such as Cutwail have gained steam. According
to SecureWorks, Cutwail now has 175,000 compromised computers under its
control, and is the top botnet to watch in 2009. Behind it on
SecureWorks' list is Rustock, which still claims 130,000 bots. The
lesser-publicized Donbot is third with 125,000 bots.
"Rustock seems to be using more domain names instead of hard-coded
IP addresses," Joe Stewart, director of malware research at
SecureWorks, told eWEEK. "Srizbi hasn't done anything; it's still down.
The others weren't really impacted for very long."
The list is further rounded out by Ozdok, Xarvester, Grum, Gheg,
Cimbot and Waledac. Together, those botnets are responsible for at
least 90 percent of spam, Stewart said.
Depending on whom you ask, the amount of spam declined 50 to 70
percent in the wake of the McColo shutdown in November. Two months
later, researchers at McAfee and Symantec say spam levels have still
not fully recovered, though their figures differ somewhat. Symantec
says the amount of spam is now at 80 percent of its pre-McColo level,
while McAfee puts the number at 60 percent.
"Spam levels haven't risen back up likely because spammers have not
been able to relocate their services to other spam-friendly ISPs
[internet service providers]," said Dave Marcus, director of research
and communications at McAfee Avert Labs. "They weren't prepared to be
taken offline and now may be scratching their heads as to how to build
more resilient operations. Our hope is that it will now be more
difficult for spammers to find other ISPs."
Some security researchers expect botnet operators to change tactics.
Botnet operators, they said, will likely look to have multiple command
and control servers to avoid being affected severely by takedowns
similar to what happened to McColo and Intercage/Atrivo in 2008.
"The McColo shutdown was a huge blow for spammers," said Dermot
Harnett, principal analyst of anti-spam engineering at
Symantec. "Spam volumes will continue to creep back up because the
profit motive still exists for spammers. As long as spammers continue
to see a return on their investments they will become even more
determined to ensure that spam reaches its pre-McColo shutdown levels
before too long."