Are you a criminal looking for vulnerable computers in a particular geographic area so that you can, say, attack a specific bank based in that region?
Or do you need some compromised computers to serve as proxies or relays?
The old days, where you had to go out and infect the computers yourself, are over. These days, you can rent part of an existing botnet for your nefarious purposes, using simple Web-based interfaces to commit your dastardly deeds.
One example is that of Vawtrak, a banking malware botnet that is also known as NeverQuest and Snifula.
"If you look at the client-side, the commands used, and the debugging code, suggests that it's more user friendly than some of the other malware we look at," said James Wyke, senior threat analyst at Oxford, UK-based Sophos Ltd.
"It's almost certainly going to be a point-and-click Web-based interface. Simplicity is one of Vawtrak's positive points."
Wyke said he did not purchase access to evaluate the platform directly since that would be an ethics violation.
Plus, actually using the platform to gain unauthorized access to the botnet's computers would be illegal.
But Sophos was able to find out quite a bit about how the Vawtrak platform works and what it is being used for, information which was released last week in a research paper.
The Vawtrak developers and their customers are targeting banks and other companies in a number of countries in a very methodical way, including custom injection code and two-factor work-arounds.
According to Sophos, it was the second most popular malware distributed by malicious drive-by downloads in September, October and November, accounting for 11 percent of malware downloads.
In the U.S., for example, the botnet targeted not only large banks such as Bank of America and Citigroup, but also smaller financial institutions not usually hit by cybercriminals -- such as Bank of Oklahoma, Cincinnati's Fifth Third Bank, the Columbus-based Huntington National Bank, and San Francisco's Bank of the West.
There are tens of thousands of computers already infected and in the network, Wyke said. That makes it smaller than some of its competitors but, because of its business model, it might actually be more profitable.
Vawtrak allows customers to request specific types of infected machines, or specific types of stolen data.
"If you want banking credentials for certain banks, or certain regions of the world, they can start campaigns targeting those banks or those countries," said Wyke.
As a result, the value obtained from each infected machine is higher than that of a typical botnet, he said.
"We're moving away from the model where the cybercriminals write their own software, or sell you a kit and you go away and create your own botnet," Wyke said.
In addition to allowing criminals to purchase specific data hijacked by the botnet, such as access credentials for specific banks, Vawtrak also allows for the delivery of new malware to the infected computers.
"This is a flexible business model," he said.
For example, the botnet's computers can be configured to serve as proxies or even -- once all the other usability has been sucked out of them -- as spambots.
"Once the machine starts sending out spam it becomes obvious that it's infected with malware and it's not going to be infected much longer," he said.
End users can protect themselves against Vawtrak by keeping their anti-virus up-to-date and taking standard precautions against phishing emails and suspicious links.
Sophos also offers a free removal tool on its website.