Researchers have discovered a major botnet operating out of the Ukraine that has infected 1.9 million machines, including large corporate and government PCs mainly in the U.S.

The botnet, which appears to be larger than the infamous Storm botnet was in its heyday, has infected machines from some 77 government-owned domains -- 51 of which are U.S. government ones, according to Ophir Shalitin, marketing director of Finjan, which recently found the botnet. Shalitin says the botnet is controlled by six individuals and is hosted in Ukraine.

Aside from its massive size and scope, what is also striking about the botnet is what its malware can do to an infected machine. The malware lets an attacker read the victim's email, communicate via HTTP in the botnet, inject code into other processes, visit Websites without the user knowing, and register as a background service on the infected machine, for instance. The bots communicate with their command and control systems via HTTP.

Botnet expert Joe Stewart says it appears to be similar to other downloader-type botnets. "It looks a lot like other downloader bots out there," says Stewart, director of malware research for SecureWorks. "It has a system for installing other malware and getting paid for it. The first stage is to get the bot piece onto the machine, and then they get paid to install other malware."

Finjan says victims are infected when visiting legitimate Websites containing a Trojan that the company says is detected by only four of 39 anti-malware tools, according to a VirusTotal report run by Finjan researchers.

"We don't have our hands on the actual [stolen] data, but we can tell a lot of what they [may be] doing with it by the malware," Shalitin says. "They can use it for spam, [stealing data], and almost almost anything."

Around 45 percent of the bots are in the U.S., and the machines are Windows XP. Nearly 80 percent run Internet Explorer; 15 percent, Firefox; 3 percent, Opera; and 1 percent Safari. Finjan says the bots were found in banks and large corporations, as well as consumer machines.

Shalitin says it appears that the botnet operators may be buying and selling bots or portions of their botnet based on a communique Finjan discovered on an underground black-hat hacker forum in Russia.

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