Corebot cleverly written botnet malware with growth potential
The malware was first spotted by IBM Security X-Force, and Damballa followed up with a deep dive into how the malware works, and what else the malware's author is working on.
The malware itself is particularly clever, said Loucif Kharouni, senior threat researcher at Damballa, in that it is written from scratch to be modular, making it easy for the author to add plugins to do specific tasks.
"Most malware is based on older malware, on Zeus code for example," he said. "This one looks like it was built new, from scratch."
In addition, it comes with a unique domain generation algorithm that generates different domain names based on where the host machine is located, making it more difficult for security companies to block those domains.
It also comes in both 64-bit and 32-bit versions, which is common for major software releases but not as common for malware.
Corebot's author is going to be monetizing this botnet in at least two ways, Kharouni said. The developer has set up an online store where customers can buy personally identifiable information stolen by the botnet. Customers can also rent individual machines on the botnet to use as anonymous proxies, buy bot source code and possibly order up custom plugins for the botnet code.
"We're still monitoring to see where it will go," he said.
He also added that it wasn't clear whether the shop will sell stolen account information from just the Corebot botnet, or from other botnets as well.
The fact that the shop has been set up indicates that there will be a lot of data coming, enough to make setting up the shop worthwhile.
As of Monday, the shop was offering around 11,000 user accounts for sale.
But it is still early days for the malware, Kharouni added.
"The author seems to be still working on it," he said. "I think the final version will come soon."
According to Kharouni, the shop is designed with a simple registration process and a payment system in which each customer gets a unique Bitcoin wallet to deposit money into.
He said it's unusual to see a malware developer also set up an online shop.
"Usually, we don't see the connection between what the criminal steals on the machines and where he sells the data," he said. "Usually, they just go on forums or, in one-on-one conversations, and sell the data that way."
There are plenty of online storefronts that offer credit card numbers or other data for sale, but in those cases it's the shop that's their primary business, he said.
Having a visible, promoted online storefront does mean that authorities may be able to take the shop down, he said.
"They do get taken down, but usually pop up somewhere else -- especially the big ones," he said. "They have the means to move around if they get taken down."
But relocating a shop does pose logistical challenges, he added, and smaller operations, once they get taken down, sometimes stay down for good.
"It really depends on whether the criminals have the means to keep the website up," he said.