Aside from the distributed denial-of-service (DDOS) attacks they launch against one another to disrupt their operations (like the recent DDOS battles between the Storm and Stration botnets), they also are constantly trying to hijack bots from one another. "Stealing is easier than building [out] one," says Danny McPherson, chief research officer for Arbor Networks, who tracks botnet activity.

ut the savvier botnets go the extra mile to protect their captor capital: Some actually "secure" the bot machines they have infected so no other botnets can steal them or utilize them, too. They install patches on their bots, for instance, to close the security holes and shut down open ports that are vulnerable to attack. "They are installing defenses to make sure no one else doubly infects the machine," says Paul Mockapetris, chairman and chief scientist of Nominum. "There are instances where a machine is infected, and part of that is defense against another infection."

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