The Federal Bureau of Investigation announced on Thursday that its ongoing crackdown on botnets, known as Operation Bot Roast, has nabbed another eight suspected bot masters in the past five months.

Calling the collection of indictments and arrests "Operation Bot Roast II," law enforcement officials boasted that the ongoing operation has uncovered more than $20 million in economic losses and discovered botnets accounting for more than 1 millions infected computer systems. The cases have been pursued by local FBI offices, the U.S. Secret Service, and -- in some cases -- international law enforcement.

"Today, botnets are the weapon of choice of cyber criminals," FBI Director Robert S. Mueller said in a statement. "They seek to conceal their criminal activities by using third party computers as vehicles for their crimes. In Bot Roast II, we see the diverse and complex nature of crimes that are being committed through the use of botnets."

Among those included in Operation Bot Roast II are:

* A federal grand jury indicted Ryan Brett Goldstein, 21, of Ambler, Penn. at the beginning of November for "botnet related activity which caused a distributed denial of service (DDoS) attack at a major Philadelphia-area university."
* A U.S. District Court in the Northern District of Florida sentenced in October Alexander Dmitriyevich Paskalov, 38, to 42 months in prison for a complex phishing scheme targeting major financial institutions in the Midwest.
* Earlier in November, John K. Schiefer, 26, of Los Angeles, agreed to plead guilty in U.S. District Court to four felony charges stemming from stealing usernames and passwords and fraudulently purchasing goods.

Botnets have become a major online threat as well as a preferred tool of many cybercriminals, which use the collection of compromised computers as a tool for spamming and fraud and to foil defenders' attempts to takedown malicious servers. Botnet groups a generally known by the software they use to infect victims' computers, including the Storm Worm and the MPack infection tool kit.

Operation Bot Roast II has led the FBI to execute 13 search warrants, including overseas, where they agency is pursing a suspect that uses the online handle "AKILL" -- the alleged ringleader of a "elite international botnet coding group," the FBI said in its statement.