(Ellen Messmer, Network World) Botnet attacks are increasing, as cybercrime gangs use compromised computers to send spam, steal personal data, perpetrate click fraud and clobber Web sites in denial-of-service attacks. Ranked by size and strength, these article presents the 10 most damaging botnets in the U.S.

1. Zeus
Compromised U.S. computers: 3.6 million. Main crime use: The Zeus Trojan uses key-logging techniques to steal sensitive data such as user names, passwords, account numbers and credit card numbers.
2. Koobface
Compromised U.S. computers: 2.9 million. Main crime use: This malware spreads via social networking sites with faked messages or comments from "friends."
3. TidServ
Compromised U.S. computers: 1.5 million. Main crime use: This downloader Trojan spreads through spam e-mail, arriving as an attachment.[...]

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