This document discusses botnets, which are collections of infected computers controlled by hackers. Botnets allow hackers to send spam emails, conduct DDoS attacks, and steal personal information. They are organized in a client-server or peer-to-peer structure. Key uses of botnets include spamming, DDoS attacks, and keylogging. The document also provides statistics on top spam-producing countries and recommends security best practices like keeping antivirus software updated and scanning attachments before opening.