More than 70 government-owned domains hit, and nearly half of the overall infections are in the U.S. 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.

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."

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