What are spam bots?

Spam bots are automated programs sending bulk email. They operate on compromised computers (botnets), cloud infrastructure, or attacker-controlled servers. Automation enables massive scale: billions of messages from distributed sources.

Botnet-based spam is particularly challenging. Thousands of infected home computers each send small volumes, evading rate limits. The distributed source makes blocking difficult; blocking one bot has minimal impact.

Defense relies on content-based filtering rather than source blocking alone. Reputation systems track bot-associated IPs and domains. Shutting down botnets requires coordination between security researchers, law enforcement, and ISPs.